PAR meter vs PAR sensor from Apogee

[timmo11]

Hi

Been looking at the posts where people have bought a PAR meter, seems like a great idea to me. I have never come across so much male cow manure as that which is claimed for expensive aquarium lighting.

Now that the group buy is over, it seems to me that if you have an electronic multimeter handy and know how to multiply by 5 in your head, then just buying their SQ-120 sensor is a much better deal at US$139 than buying the whole meter for $250. In fact you could easy buy a multimeter for US$110 and have a lot of change left over.

Any counter arguments to that?

Tim

[shoggoth43]

Tim,

Any luck on this? Which did you go with? I think I found the basic meter online for 200$ but saving some green is always good.

-
S

[timmo11]

Tim,

Any luck on this? Which did you go with? I think I found the basic meter online for 200$ but saving some green is always good.

-
S

Hi Shoggoth

Yes I went for the sensor. I spoke to a very helpful woman from Apogee who told me that the sensor was identical to the one on the meter.

It worked fine with a multimeter. One thing to watch out for is that the wires are bare. The sensor is putting out a voltage all the time, so you don't want them to short. When it is sent to you, it has a cap over it to keep the voltage down to almost zero. Once you have it it would be worth soldering at least one of the bare wires into some kind of plug or socket to stop it shorting.

I ended up plugging mine into a labjack and just graphing it on a PC, but most people will probably want to move it around their tank a bit and see what the levels are. In any case, so long as you have a multimeter which can measure down to at least 0.2 mV , and you can multiply by 5 in your head, you will be fine.

Tim

[JDowns]

This is probably the route I'm going to go. Since labjack is open source it wouldn't be to difficult to customize a plugin to make the whole process of data logging and interpreting the data.

I don't see the problem with moving the sensor around the tank though? Sensor is wired to the labjack then to the pc via a usb, this shouldn't inhibit moving the sensor around the tank though. Only difference I can see in this scenario is that the labjack is wired to the pc, which shouldn't block mobility of the sensor. Unless I'm missing something obvious here.

[VaughnH]

It would be very nice to see a photo of what you get when you just buy the sensor. I'm having a hard time picturing the "bare wire" aspect of it. Also, is the filtering, or whatever method is used to make this a PAR sensor and not just a light sensor, in the sensor?

[SuperColey1]

Pictures for you H:

Midland*Reefs*Ltd*::*Apogee... (http://www.midlandreefs.co.uk/xcart/home.php?cat=269)

AC

[JDowns]

From what I gather from Apogee's spec sheets the sensor is what is calibrated. The meter is just that, a conversion unit and a datalogger. A labjack should be able to take place of the meter.

[VaughnH]

Pictures for you H:

Midland*Reefs*Ltd*::*Apogee... (http://www.midlandreefs.co.uk/xcart/home.php?cat=269)

AC

Good! Thank you. I wonder if it is economical to buy a mV meter to be dedicated to the sensor, something I feel too lazy to look up for myself.

So, it is the stuff inside the sensor head that makes it measure PAR and not some other form of light intensity. That should trigger someone's creativity and result in something even better than the complete unit.

Sort of on topic: what does the screw in the back of the sensor do?

[JDowns]

I like the idea of the labjack. You could expand off of it with other sensors as long as you know the voltage outputs and have it all monitored on a pc. The open source environment really makes it appealling as well. You could monitor Temp, PH, O2, CO2, control lighting / dimmable also, water height, water spills, etc. Could be fun to play around with different things.

[JDowns]

Sort of on topic: what does the screw in the back of the sensor do?

I would think the screw is for mounting the optional leveling plate.

[Tom Barr]

I like the idea of the labjack. You could expand off of it with other sensors as long as you know the voltage outputs and have it all monitored on a pc. The open source environment really makes it appealling as well. You could monitor Temp, PH, O2, CO2, control lighting / dimmable also, water height, water spills, etc. Could be fun to play around with different things.

Ideally, it would be nice to have a simple all in one unit that is able to data logs and interface with graphing software automatically both fro control and monitoring.

pH
Redox
Temp
CO2
O2
light/timers/dimmers
water levels
Water spills
Feeders
Dosing
Automated water changer

Etc

Not much more than temp, CO2, dosing, light and water changers for 99% of folks in planted tanks.

So 5 main parameters.
You could use the probe to dial in the PAR you want, if you had a suspended bar and a small motor to raise and lower the light, then that could function as a dimmer as well.



Regards,
Tom Barr

[VaughnH]

I would think the screw is for mounting the optional leveling plate.

Yes, it does look like that is what it is for. Right now I have our local club's PAR meter, so I may get my nerve up and remove the screw to see if that is the case - it looks 99% certain. Then it will be easy to make a simple and rugged holder for the sensor to make it easier to take measurements at various locations in the tank.

[JDowns]

Since I"ve been dying to know what my par readings are I ordered a U3 Labjack and a quantum sensor.

Be interesting to see what levels these "highlight" plants are actually growing at, and not assuming I have low, med, or high light.

I'm more curious about my non CO2 tank than anything else, with PC lighting.

I'll also be able to measure some Tek fixtures.

[VaughnH]

The more PAR data we get, when it includes the lighting specs, the distance between the light and the sensor, and how the PAR varies as you move it around the tank, the more accurately we will be able to guess what any given light fixture will do on any other tank. So, be sure to get good data, and, PLEASE, report it here.

[JDowns]

Labjack will be here tomorrow so I can start playing with the software right away. I'm hoping the graphing doesn't take to much modification, but with Apogee's lead time for shipping (2-3 weeks), I'll have plenty of time to do any modifications.

It would be nice to have some type of graphed database.

At what par would be considered in a "rough" manner, low, medium, and high?

I'm assuming right now without seeing anything that the sensor will be outputing a constant reading through the meter (labjack). I'll probably have to have an output that I can view and a push button type device used to capture a logged output on a predetermined plot. This is going to take a little pre planning.

[JDowns]

To keep the contacts safe from water, I decided to enclose the Labjack in a hobby box, and add a viewing window of acrylic to view the LED status light. The USB cable hole was drilled and a rubber grommet was used to seal that port. Once the sensor arrives I'll do the same for that wire. Although I might use a quick disconnect type scenario. I'll have to make a trip to Radio Shack or Fry's Electronics and see what I can come up with since I like the idea of being able to easily disconnect a component and have the contacts water resistant.

Now that the unit is water resistant I'll start playing around the with software.

http://www.plantedtank.net/forums/members/jdowns-albums-misc-picture1479-labjack.jpg

[JDowns]

The more PAR data we get, when it includes the lighting specs, the distance between the light and the sensor, and how the PAR varies as you move it around the tank, the more accurately we will be able to guess what any given light fixture will do on any other tank. So, be sure to get good data, and, PLEASE, report it here.

I absolutely agree and will post all findings.

Reason I ask what is considered low, medium and high par. Would be so we can graph accordingly. I would think a par spectrum if you will. Use a standard BGR spectrum. Blue being low par, Green being medium par, Yellow being high par. That would help differentiate zones. Then we can sort plants properly by PAR rather than WPG rules.

Now I understand there are many factors that can influence par. Covers / cleanliness, turbidity, surface agitation, tanins, reflectors, etc. But given the wide range of par plants adapt to, we should still have some wiggle room, but these factors have to be taken into account.

Plus as you have noted, the more data we can gather, the better understanding we can have for a given fixture, and the better understand we can gain.

[VaughnH]

PAR numbers are even more complicated than high, medium and low. PAR increases as you get closer to the light source. In fact for most relatively small dimension sources it varies inversely with the square of the distance. So, there is no one PAR number that characterizes what the light is providing for the plants. It can be 50 micromols at the substrate, 150 micromols half way up in the tank, and 250 at the surface. I think we are going to be stuck with considering just the substrate level PAR and the height of the fixture from the substrate (which then determines the PAR higher up in the tank.) Any other scheme seems to me to get so complicated no one could use it.

[JDowns]

I think it would be interesting to see what a daily / weekly cycle would look like as far as PH, O2, Redox, and temp. Maybe even TDS and Conductivity in the future along with CO2 (not jumping off the cliff just yet :rolleyes: ).

How reliable are the nitrate probes? This would also be intriguing to guage uptake rates.

[JDowns]

The more PAR data we get, when it includes the lighting specs, the distance between the light and the sensor, and how the PAR varies as you move it around the tank, the more accurately we will be able to guess what any given light fixture will do on any other tank. So, be sure to get good data, and, PLEASE, report it here.


Can we agree on the parameters for testing. Where data is collected and how many spots. Obviously plant mass is going to cause some interference here. But if we have a standard, then we can database the findings better and create one thread with all the information.

I can test on my 150 all sorts of bulbs, Aquaflora, Midday, Aquablue, 10000k from Catalina, and in alot of configurations, from 80w to 480w. Then on the 29g biocubes the pc's.

At the lfs I can test a myriad of different fixtures. Everything from a few ADA fixtures with MH, Tek 4ft 4-bulb, Archea light fixtures for nanos in all sizes, and a few other fixtures they have up and running.

Sensor should be here tomorrow or Friday, so I planned to do some measurments over the weekend.

[VaughnH]

The readings of most interest to me are PAR at the substrate level in the center of the tank, or right below the light fixture (the thickness of the sensor above the substrate), at some specific distance above the substrate at the same middle location, and roughly how the PAR varies as you move from end and front to back. Of course, all of that for a given distance between the light bulb and the substrate. If possible, it is very useful to have the substrate level PAR with the fixture raised or lowered a specific distance. As I see it, those are the best data to standardize on, and the data that let you determine how high a given fixture has to be to get some PAR value.

[JDowns]

The readings of most interest to me are PAR at the substrate level in the center of the tank, or right below the light fixture (the thickness of the sensor above the substrate), at some specific distance above the substrate at the same middle location, and roughly how the PAR varies as you move from end and front to back. Of course, all of that for a given distance between the light bulb and the substrate. If possible, it is very useful to have the substrate level PAR with the fixture raised or lowered a specific distance. As I see it, those are the best data to standardize on, and the data that let you determine how high a given fixture has to be to get some PAR value.

Well its xmas in July. Sensor finally made it. Initial test with a m-meter and sensor seems to be intact. Modified a Kent Pro Scraper with a mount for measurements.

Those parameters for testing seem simple enough. I'll test my tanks this weekend. Talked with the lfs today and they are good with me coming in Monday and getting some data. There are seven different unique fixtures over display tanks that I can measure, from nano's to 80g, pc's, t5's mh, and hot5's. Which should give a good array of data.

[SuperColey1]

try and take a note of the water clarity in each tank too. Can make a difference

AC

[JDowns]

Just fiddled around before going out for the night and I'm somewhat amazed at what I figured was lower lighting. But it does re-affirm any advice I've given that 240w HOT5's over a 2ft deep 5ft tank is more than enough light. Center of the tank 20" below water line, bulbs 16" off the waters surface, and through 1/2" of acrylic. 70-75mmol's :eek: 160w 45-50mmol's.


I'm going to have to try alot of variations with this setup to help get a feeling for what raising / lowering a light fixture does in relation to par.

[Tom Barr]

Stop HLD!

Regards,
Tom Barr

[SuperColey1]

you'll probably find that having the light lower means very high PAR underneath the tube(s) and lower light in other areas.

Raising the light will definately reduce PAR directly under the tube(s) but more than likely you will see a more even spread across the tank and possibly evn find higher PAR in the areas that were showing low when the lights were lower down :)

[JDowns]

Stop HLD!

Regards,
Tom Barr

Just initial logging is showing me that we highly underestimate our lighting. It really is no wonder so many people have so many problems when they are recommended lighting that is far far to much than is actually needed. HOT5's really do put out a great deal of light. Even my PC's in the 29 shocked me at the par levels, shallow tank yes, but still given the trend I'm seeing on fall off with distance, much higher than I would have thought.


you'll probably find that having the light lower means very high PAR underneath the tube(s) and lower light in other areas.

Raising the light will definately reduce PAR directly under the tube(s) but more than likely you will see a more even spread across the tank and possibly evn find higher PAR in the areas that were showing low when the lights were lower down :)

THere definatly is a reduction, not a huge amount, but by percentage a noticable effect. Raising the light does definatly give you higher par in what where lower areas with the change in height of the lights. One interesting point has been much higher light at the substrate along the front edge of the glass with the lights raised.

I recorded today 10 different scenarios with the large tank and three scenarios on the 29. I won't have the luxury at the LFS since all their fixtures but one are fixed height. But the additional data of seven different light fixtures should give a nice range of data. Add that to Hoppy's and Tom's data and others on this forum, we should start to get a really good idea on light levels.

[VaughnH]

Just fiddled around before going out for the night and I'm somewhat amazed at what I figured was lower lighting. But it does re-affirm any advice I've given that 240w HOT5's over a 2ft deep 5ft tank is more than enough light. Center of the tank 20" below water line, bulbs 16" off the waters surface, and through 1/2" of acrylic. 70-75mmol's :eek: 160w 45-50mmol's.


I'm going to have to try alot of variations with this setup to help get a feeling for what raising / lowering a light fixture does in relation to par.

Very good data! I'm starting to plot your data, so please, do post your other PAR data too. Right now I am most interested in data at the center of the tank, under the bulbs, from substrate level on up. Nothing in the first three data points surprises me at all, and it tends to confirm my belief that the longer T5HO bulbs give about the same PAR at a given distance no matter which wattage bulb you have, with the longer bulbs needed to cover longer tanks.

[JDowns]

I've got it all plugged into a spreadsheet. I'll be at the LFS tomorrow afternoon
and I'll update the spreadsheet then and post it up.

Data I'm collecting.


Tank Gallonage
Tank Dimensions
Light Manufacturer
Bulb Configuration (wattage and number of bulbs)
Bulb Type (ie PC or T5)
Distance / light to water surface
Distance / light to substrate
Par just under water surface center of tank
Par middle at center of tank
Par at substrate at center of tank
Par variation throughout middle region of tank
Par variation throughout substrate region of tank
US gallons inches inches inches umol umol umol umol umol

[Tom Barr]

Just initial logging is showing me that we highly underestimate our lighting. It really is no wonder so many people have so many problems when they are recommended lighting that is far far to much than is actually needed. HOT5's really do put out a great deal of light. Even my PC's in the 29 shocked me at the par levels, shallow tank yes, but still given the trend I'm seeing on fall off with distance, much higher than I would have thought.


So what say you to folks running around insisting on 3-4w/gal of PC/T5 lighting for gloss and dozens of other plants?

When you are wrong, and way off, never bothered to test anything, then howl about EI and not testing being bad, wasteful etc, then look the other way with light...........sort of want to beat them a stick, one embedded with "logic nails" that can penetrate their thick skulls.



THere definatly is a reduction, not a huge amount, but by percentage a noticable effect. Raising the light does definatly give you higher par in what where lower areas with the change in height of the lights. One interesting point has been much higher light at the substrate along the front edge of the glass with the lights raised.


So comparing the heights of various aquarist makes a huge difference as well, not just the Micrmols, rather the effective spread and evenness factor over the bottom, if it's off by more than say 20% empty, it should be changed IMO.

Regards,
Tom barr

[Tom Barr]

Bulb age if possible.
Then go back 6-12 months.



I've got it all plugged into a spreadsheet. I'll be at the LFS tomorrow afternoon
and I'll update the spreadsheet then and post it up.

Data I'm collecting.


Tank Gallonage
Tank Dimensions
Light Manufacturer
Bulb Configuration (wattage and number of bulbs)
Bulb Type (ie PC or T5)
Distance / light to water surface
Distance / light to substrate
Par just under water surface center of tank
Par middle at center of tank
Par at substrate at center of tank
Par variation throughout middle region of tank
Par variation throughout substrate region of tank
US gallons inches inches inches umol umol umol umol umol

[VaughnH]

Bulb age! The one variable I always forget. Ideally all of the data any of us collect would be from bulbs 3-6 months old.

[SuperColey1]

Or although its to likely possible, data from bulbs of many ages to see if they really do deteriorate as some people would have us believe or if they keep 95% of their PAR over 8000 hours as that article suggested r.e. maintaining 95% of lumens (on electronic ballast.)

AC

[JDowns]

I'll add in bulb age. I'm gonna have to approximate mine at about 8 months. Due to actual usage from testing different scenarios for coloration (which is why I have a large selection of bulbs), and settled on a Aquaflora / Midday Mix. But I could purchase 3 aquafloras and compare new to old. Although I suspect like SuperColey there wouldn't be much of a difference. I think there might be more of a difference across cooled fixture and non cooled fixtures.

I was also suprised to see that the 1/2" acrylic doesn't do much to lower par. At an inch below the surface where I took all Top Center measurements, if I venture to the open area par only increased by 1 - 2 units. So not a significant difference.

I agree Tom. The advice for lighting really is a shame. Folks act like foregrounds or these so called high light plants were never grown before the advent of PC's or T5's. So we couple plant databases and advice that some plants are "high" light with miconceptions of how much light is actually in the tank, and we end up with people with lots of problems. Then they end up chasing nutrient deficiencies based on terrestrial plants that completely ignore Carbon and are factually incorrect in assumptions, and then you have more problems. Then you get the folks that just echo these things ... and the wheel keeps on turning.

Hopefully we can get enough data to see a trend. Then better advice can be given.

One thing that is very interesting to visualize with the meter. Is the effect of how par changes vertically. This is obviously more drastic in shallow tanks. If we look at how the levels change as far as percentages. You can easily have 50%+ gain in par over the span of a stem plant from planting to trimming. Then look at how that affects the need for Carbon. Now given our already high light, its easy to see how CO2 can be adequate early in the week and defecient later in the week. Then magnify that by a tank full of plants. Then add in to the thought process of flow and circulation. I can easily see now why you harp on CO2 and circulation as much as you do.

Hopefully as more data is gathered, we can also have a optimum distance between light and water surface. Now my tank will be different, due to spacing of the bulbs. I use alternating bulbs. Six bulb fixture and i only use every other bulb. I'll have to test that effect with just the center bulbs to simulate a typical four bulb fixture, since configurations here will have an effect.

[JDowns]

An example of the changes in verticle par. I just trimmed the other day a stand of Limno Mini and replanted. Tops of the plants are at 55 mmol. From where I trimmed they were at 85 mmol. Thats a 55% increase in light intensity. Now what does that due to nutrient demand. These are issues to be aware of as things grow in, and how you might not have issues with CO2 one week but have them the next week.

[VaughnH]

The huge variation in PAR going from substrate to water surface is one good recommendation for MH lights, hung a good 24 inches above the tank. That height greatly reduces the intensity gain as the plants grow higher. I'm inclined to see the "perfect" light fixture as one that is the same outside dimensions as the tank, with many small lights (LED or full length T5 tubes?) evenly spread out over the entire fixture surface, with that fixture many inches above the tank. With this you get much closer to uniform intensity all over the tank.

[JDowns]

Just got back from measuring. Pretty much what I expected as far as ranges. The ADA NA-Green bulb in a current fixture was interesting. The wide range with lights closer to the waterline was confirmed. Great deal of fall of around the corners and edges. The Tek 4 bulb was a shockers, I had to go back and confirm measurments on other tanks to make sure the sensor didn't get borked. After that re measured. Tons of light out of that fixture. Even two bulbs was a great deal of light.

I'll plug in the data and put it in a pdf for ease since I utilize OpenOffice and I'm sure not alot of people have MS Excel.

[VaughnH]

Just got back from measuring. Pretty much what I expected as far as ranges. The ADA NA-Green bulb in a current fixture was interesting. The wide range with lights closer to the waterline was confirmed. Great deal of fall of around the corners and edges. The Tek 4 bulb was a shockers, I had to go back and confirm measurments on other tanks to make sure the sensor didn't get borked. After that re measured. Tons of light out of that fixture. Even two bulbs was a great deal of light.

I'll plug in the data and put it in a pdf for ease since I utilize OpenOffice and I'm sure not alot of people have MS Excel.

A pdf would be very nice. I'm not sure how to attach a pdf to a comment here though.

[JDowns]

Made this easier than a pdf. Converted to threer file formats. An html document, OpenOffice document, a Excel 97 document. OpenOffice is a free Microsoft Office like suite. A pdf would be difficult for what you want Vaughn.

HTML (http://members.cox.net/just_me/Par%20Data.html)
OpenOffice (http://members.cox.net/just_me/Par%20Data.ods)
MSExcel (http://members.cox.net/just_me/Par%20Data.xls)


Its just too much to fit into an image properly. I'll see what I can do on that end.

I missed this in the notes. GMix is a Geissemann mix of Midday and Aquaflora on everything but the IceCap fixture which is a mix of Aquaflora and Aquablue.

[VaughnH]

Thank you very much! I use a Mac Intel computer so I can open any of the three versions, and I have an Open Office program too. I chose to open the Excel version. Now, to have some fun plotting all of this stuff.

[JDowns]

NP. Hopefully we can add more and more data over time.

For me its been interesting to see the wide range of lighting, and more important just how high lighting can be. Its made me rethink how things are actually working. I think just the visualization of the data in my hands helped open my eyes to the lighting aspect of this hobby.

I have to mention a huge thank you to the folks at AquaTouch for allowing me to come in and poke around the tanks. Great local shop with good peeps.

[SuperColey1]

I agree Tom. The advice for lighting really is a shame. Folks act like foregrounds or these so called high light plants were never grown before the advent of PC's or T5's. So we couple plant databases and advice that some plants are "high" light with miconceptions of how much light is actually in the tank, and we end up with people with lots of problems. Then they end up chasing nutrient deficiencies based on terrestrial plants that completely ignore Carbon and are factually incorrect in assumptions, and then you have more problems. Then you get the folks that just echo these things ... and the wheel keeps on turning.

I agree totally. Being pedantic you could say that plants currently called 'high light' plants like HC and Glosso are in fact low light because they never see highlight. lol

They do grow in the low light area however while I concede that highlight is needed to provide low light at their level I suspect though that it is getting the CO2 to the substrate level that is the important thing to them. After all I've never seen HC or Glosso grown in highlight non CO2 tanks. Therefore the question would be (another topic really) how much light they need if indeed any more than the traditional 'low light' plants like Anubias/Ferns when high CO2 is supplied!!!

With the bulbs I suspect that they will probably lose the 5% suggested in their first few weeks of use while they 'burn in' and then stay pretty constant for a long long time. much longer than 6 months/1 year unless used on the old electric/magnetic ballasts.

Keep the info coming ;)

AC

[Tom Barr]

Its made me rethink how things are actually working. I think just the visualization of the data in my hands helped open my eyes to the lighting aspect of this hobby.


Such insights are really the ground breakers.
Rethinking the assumptions you had is good.

This is more meaningful than some minor tweak and claims that it solved algae or plant growth issue ( questionable effects at best, and only small possible effects), this is huge.

It's much like adding PO4, or realizing non limiting nutrients for plants does not = algae. Test are great, if you use them to answer the larger questions.
Also, if you start with a general model of how plants grow, light is where it all starts and then you can reduce work/labor, increase efficacy of the resources put into the aquarium to eliminate waste, use "just enough" for light, CO2, and.......nutrients.

As was the case with PMDD, they chose one nutrient to limit,then make sure that the others are non limiting. Here, we apply this this same concept of Liebig's law, but we now expand it and include light, CO2....and nutrients.

We can limit nutrients to reduce rates of growth, but waste a lot of light(which is the largest $ factor in the operation over time) and increase algae risk and stunting and increased demand for CO2. If we reduce light, this reduces the risk of algae and reduces the demand for CO2 and every nutrient.
So this makes for a much better choice if this is a goal.

The "evenness spread" I think is also key and much more natural to what plants are typically exposed to. The real hot spots will demand much more, the weak spots much less, this can occur on the same plant!

If things are more even, then you get more even growth and less localized issues.
Some ask why some plants do poorly, while others are growing well, the answer might be due to this lack of evenness.

Add CO2 localization issues, current etc, now we can see a much larger picture.
Then you tie CO2 and light together.

Nutrients are fairly easy by comparison, they are even throughout and do not change much, we add enough (water column + sediment either or or both)and that's it.

Then you tie all 3 together.
Now you have a full model to work with.

Regards,
Tom Barr

[Tom Barr]

After all I've never seen HC or Glosso grown in highlight non CO2 tanks. Therefore the question would be (another topic really) how much light they need if indeed any more than the traditional 'low light' plants like Anubias/Ferns when high CO2 is supplied!!!
AC

There is already an answer to your question posted by Ole and Claus etc from Tropica.

When we add CO2, the light efficiency use is increased, so we can grow plants at lower light using CO2, than we can with non CO2 methods (***the reverse it what many assume***).

Why? Simple. The plants need less resources for acquiring CO2 since there's plenty available, so they can focus more on gathering minimal light. When there's little CO2, they need more Rubisco to fix CO2 and scavenge any tiny amount of CO2 gas. so that's less resources available for light capture.

Tropica (http://www.tropica.com/default.asp)

Click on "Aquaristic", then "The Biology of water plants", there's A SIMPLE STUDY on CO2 and light. There's also a good article on light right in the main section, "Light: the Driving Force" etc.

Basic stuff, all there available from a group of aquatic plant folks and growers that operate the largest aquatic plant horticulture grow out area in Europe.

Might help you support what you are/will be saying elsewhere to more skeptical folks.

Regards,
Tom Barr

[SuperColey1]

cheers Tom.

From that the 'high light myth' has now been banished in my eyes. ;) Unless of course, its a non CO2 tank :D

AC

[VaughnH]

So much data, so little time!

Here is the T5HO data plotted on a log-log graph, which makes seeing the relationships between the variables easier. The two lines with different slopes are the inverse square relationship and the direct proportionality relationship, between distance and PAR.
http://i573.photobucket.com/albums/ss176/Hoppycalif/JDownsPAR.jpg

It looks very much like the inverse square relationship holds when the T5 bulbs are relatively close together compared to the distance to the sensor, but not when the distance is reduced too much.

I was curious to see if the different length bulbs and different manufacturers would have a different efficiency. To do that I "normalized" the data to get PAR at the same distance for each fixture. From that I got a surprise: the Ice Cap fixture gives twice the efficiency as the others - at a given distance and wattage the Ice Cap fixture gave twice the PAR of the others, which were all about the same. I didn't expect that, and I expected the Tek fixture to be the best, just by reputation. Also, the Archaea fixture, which uses a "hammered" reflector finish instead of a mirror finish, and was the shortest of the fixtures, had about the same efficiency as the Tek and Catalina fixtures.

More to follow.

[Philosophos]

Wow, nice info there. Also more evidence that these new T5HO's are completely over watted for most aquariums. You really should compile all your PAR data in to one place; I've found it to be extremely helpful.

-Philosophos

[Tom Barr]

cheers Tom.

From that the 'high light myth' has now been banished in my eyes. ;) Unless of course, its a non CO2 tank :D

AC

Counter intuitive don't you think?
More light is required for non CO2 methods?

But this has some limits, a little bit more light to make up for the loss in energy, but more light nonetheless at a lower end of the scale, at the higher end, this does not work since plants are really stressed from strong CO2 limitation.

Still, folks with low light, should certainly invest in CO2, not more light, and adding CO2 does not imply you also need more light either, the reverse is actually true. Both are a bit ground breaking in concept, but the evidence is quite clear from myself, you folks with light meters, Tropica, and basic research on CO2 and light.

Now folks should try and convince what I and George Booth have been trying to tell folks for decades, you are fine with 1.5-2w/gal.

Maybe less if the light is T5, PC etc.....

This is as myth defying and ground breaking as adding PO4, perhaps more important in many respects, as it will help any method.

Regards,
Tom Barr

[Tom Barr]

That icecap did very well on that graph.

The clear winner if efficacy is your game.
Where's that Detlef feller?

Haha, he likes PUR and PAR, this should help focus a lot more emphasis on the efficacy of the light on a different level we can measure and compare, and perhaps get much more use/efficiency out of vs trying to compare bulbs etc.

I use Tek on 2 of my tanks, I'm honestly thinking of going all T5, but they do not make a 6 ft hood, I'd have to use 2 36" long hoods for the 180.

Catalina lights did pretty good. Tek did better.
Good graph Vaughn.

We should do this for PC lights, they are not going anywhere for awhile.
If you need some MH, HQI's, I have those(don't use them anymore though)


Regards,
Tom Barr

[SuperColey1]

Counter intuitive don't you think?
More light is required for non CO2 methods?

I phrased that badly. A little sarcastic maybe.

What I mean is some plants 'can't be used' in non CO2 tanks not because they have high light demands but because they have high CO2 demand :)

After all even DW admits there are many plants she can't grow in her NPTs even with what we would consider is pretty reasonable lighting at the 1.5 - 2WPG region.

AC

[JDowns]

Some additional notes to add.

On my fixture when I use 240w the bulbs being used are 3" apart. The Icecap data should also be noted at a 4" spacing between bulbs. Spacing of the bulbs farther apart also will play a role in better effeciency in spread.

I was surprised at the data on the Icecaps. I'll have to find out which ballast is used. The intensity of the Tek was surprising, I wouldn't have thought that much higher. Even with two bulbs. I can start to see a trend where a fixture should be raised to a minimum distance from bulbs to water surface just to even the spread of light while also decreasing intensity. Depth of tank in relation to depth of fixture is also notable. This is where the Archaea fixture did poorly in spread.

Nice graphs Vaughn. That makes putting things in perspective much easier.

A seperate thread in the Articles section would be nice. So we can have all the data in one spot.

I'm really tempted to go to the box store and get a T12 and T8 4 bulb fixture and test them over the tank this weekend. Fixtures can get returned after use :P. Be interesting to see the relationship of light intensity there compared to T5's and PC's

I'll be remeasuring the Icecaps every three months at the stores request. They are very curious at the longevity of the bulbs. Since there are 50 bulbs in use on the same type of setup on all the sales tanks. This will give them a much better replacement schedule. While also noting for us a usable guideline for longevity.

[JDowns]

The "evenness spread" I think is also key and much more natural to what plants are typically exposed to. The real hot spots will demand much more, the weak spots much less, this can occur on the same plant!

If things are more even, then you get more even growth and less localized issues.
Some ask why some plants do poorly, while others are growing well, the answer might be due to this lack of evenness.

This was part of the eye opener for me. I've seen it discussed that a plants health in various parts of the tank could be due to light issues. So it was interesting to see just how varied par can be in a localized area, especially as you travel to the corners.

If you consider a scenerio where CO2 concentration is borderline, how the variation in light intensity can have such a dramatic effect on plant health.

This really makes observing a tank much more concise. Best investment I've made next to the pump upgrades ;)

[JDowns]

The IceCap is a 660 ballast with IceCap T5 reflectors. I'll update my notes to show this.

[jeremyh]

We should do this for PC lights, they are not going anywhere for awhile.


I just got my Apogee meter, I'll do a whole suite of measurements on my 77gal (48x16x24) tank - it has a Coralife Lunar Aqualight 4x65W PC fixture over it.

I'll be taking readings for 2x65W 6,700K; 2x65W 10,000K; and with all 4 tubes on. I probably won't be able to take readings with varying height above water, though - the light is on those spindly plastic legs.

(Quick preliminary readings, though, show the 10,000K tubes to be significantly brighter than the 6,700K tubes - approx. 46 v 35 umol at the substrate)

Stay tuned - it may take a few days for me to find the time to do this properly, this aquarium is at my office and things are pretty busy right now at work...

Cheers,

~Jeremy

[VaughnH]

I'm having loads of problems trying to get on the Internet, so this is a day late:

For some time now I have believed that the only thing that has a major effect on light intensity in an aquarium is distance from the bulb - for a given light fixture. In other words, it doesn't matter if a 24 watt T5HO light is over a 10 gallon or a 100 gallon tank, the intensity at 10 inches or 20 inches is the same. This has to be true unless the glass sides of the tank reflect a substantial amount of light to increase the intensity. And, I don't believe that they do.

Also, I believe that T5HO bulbs, longer than some minimum length, all give the same intensity at a given distance from them. The added wattage of longer bulbs just allows those bulbs to provide that intensity over a longer length under the bulbs.

I decided to try this great set of PAR data to see if my idea is correct. First I plotted the data this way:
http://i573.photobucket.com/albums/ss176/Hoppycalif/PARvsDistance.jpg

This collects the data from the 2 bulb, 4 bulb, etc. fixtures and treats them as if they were all from the same fixture. Then I used the "inverse square" line to get the intensity for 2 bulb, 4 bulb, etc. fixtures at the same distance from the bulb, and replotted that:
http://i573.photobucket.com/albums/ss176/Hoppycalif/PARvsNoT5s.jpg

As you can see, these data points all fall on a straight line, or close to it. From this I conclude that my theory is likely to be correct - T5HO bulbs give the same intensity at a given distance, whether the bulbs are short or long, as long as they are longer than some minimum length.

The value of this is that when you have a new tank and want to figure out how much T5HO light is needed, you can determine that from known data from other different length T5HO bulbs, and just get the T5HO bulb that is the same length as the tank (or use two shorter ones end to end). This greatly simplifies the process of selecting the "right" lighting. This also shows that 4 bulbs give about twice the intensity as 2 bulbs, etc.

Higher up in the tank, closer to the bulbs, the intensity no longer follows the inverse square relationship, so this is most useful for larger tanks, and with the bulbs in fixtures hung above the tank, not sitting right on top.

Using this idea, one would pick T5HO fixtures either the same length as the tank, or two of them end to end equaling the tank length. Then pick a one bulb fixture, if the tank has a front to back dimension less than 12 inches or so, but pick multiple fixtures, mounted some distance apart, if the tank is deeper than that. If the tank is too high to get adequate intensity from one T5HO bulb, one would use a fixture with two bulbs, mounted close together, and multiples of that if the tank has a larger front to back dimension. If one wants to avoid having low intensity at the substrate, but very high intensity at the water surface, one mounts the fixtures high above the tank, at a distance equal to the tank height, for example, and uses multiple bulb fixtures.

One more thought: The Ice Cap light doesn't show up as being nearly as superior when the data is presented this way. And, the relatively crude Archaea light doesn't seem nearly as good. This is more like what I would expect.

[Tom Barr]

This was part of the eye opener for me. I've seen it discussed that a plants health in various parts of the tank could be due to light issues. So it was interesting to see just how varied par can be in a localized area, especially as you travel to the corners.

If you consider a scenerio where CO2 concentration is borderline, how the variation in light intensity can have such a dramatic effect on plant health.

This really makes observing a tank much more concise. Best investment I've made next to the pump upgrades ;)

Well, I think most everyone had thought it was even to begin with and not so varied. When you get data that suggest that there is this higher degree of variation and patterns, then it starts to make more sense how we have such differences.

Some claimed this to be all due to nutrient differences in their tanks and tried to manage it that way. However, many others, myself particularly, never found such differences. Other tanks had them here and there, so something else besides nutrients was occurring, so CO2 and light needed some strong good re examination, not just accepting of the same old tired claims, myths and dogma.

I just got irritated when these same folks who promote testing for N and P, wanted to cling to the old ways when it came to light and accept what had been written and try to use a poor peusdo EI style estimation, and not test.
To top that off, then they also suggest that you and others need really high light watts.

These clowns are as far as the ones that use to claim excess P or N = algae blooms. Perhaps even more so.

This needs changed and supported well to help other folks not learn this garbage, not get in the habit of repeating/spreading it all over the web.
Then we will get somewhere and folks can better focus on their goals, have less algae issues, increase efficiency, less overall and operating cost, better even plant growth, less stress to fish etc.............

New hobbyists fall into these same folks telling others this backwards crap, then listen to the BS about nutrients.

They miss the big 2 issues, CO2 and light ........and micromanage nutrients.
Only when you addreass the light/CO2, can you fairly consider and look at nutrients.

All this stuff ties together.


Regards,
Tom Barr

[VaughnH]

Expanding on my post above: I believe all tubular bulbs, which are about the same length as the aquarium, give the same PAR at a given distance from the bulb. That means a T12 bulb 48 inches long gives the same PAR as a 24 inch long T12, and the same is true for a T8 or T5 bulb.

To convince myself of this I did a simple calculation of the intensity versus the length of a linear bulb, directly under it, which totals up the light from directly over head and the light from each increment of bulb length on that same spot. That gave me an equation:
Intensity is proportional to the arc tangent of (the bulb length over 2x the distance from the bulb). And, barring mistakes, this gave me this curve:

http://i573.photobucket.com/albums/ss176/Hoppycalif/PARvsTubeLength.jpg

Most commonly used tanks are from 1.5 to 3 times as long as they are high. So, the intensity for a bulb the length of the tank would range from about .7 to about .9 (units are irrelevant), which for all practical purposes is the same number. It is only on non-standard tanks, the very long, but still only 20 inches or so high tanks, or the extra high tanks, like a 20H tank, which would fall outside of that range.

To me that says I wasn't quite correct above - a T5HO bulb the same length as the tank gives the same PAR at the center at the substrate for all standard shape tanks, until the bulb length is short enough that much of the length is wasted length, where the electrodes are. And, the same is true for all other linear tube bulbs. But, for non-standard shape tanks my idea wasn't correct.

So, if you want "low" light a T12 or T8 bulb at the top of the tank will give it. If you want "high" light a T5HO bulb at the top of the tank will give it. If the tank is "deep" - front to back - you need more than one of those bulbs, widely separated to get that light reasonably spread over the whole substrate, and not starving the upper front and back areas for light.

Missing is the data for T12, T8, T5NO bulbs for PAR at the substrate, to verify this. And, of course, then there is the PC bulb, a dual linear, but generally short vs the tank length bulb.

Are we having fun yet?

[Dutch]

Do we have an updated thread on this data, or where I can download it?

Thanks,

Dutch

[dutchy]

You can have look at TPT, Hoppy's post in the Lighting section on PAR data for T5 and other fixtures.