Just wondering if anyone realy knows why (in general) you can get away with rediculus high light levels in nano's.
I have had experiance of this, my pico 8lt planted has 19WPG with presurised Co2 and did realy well, my best yet.

What hapens to the WPG rule when looking at pico/nano aquariums? Why does it work?

Cheers,
Graeme.

The Watts per gallon (WPG) rule usually works, but begins to stop working in smaller and much larger tanks. Let's say I get a 1 gallon tank, and I put a 5 watt bulb on it. Well, I have 5 watts per gallon, why can't it be used? Reason: 5 watts is dimmer than you will need to grow plants.

There is no theorectical reason why watts per gallon is a valid parameter for how much light plants need. It just happens to be an easy number to determine for any given light fixture, and coincidentally, it can be used to approximate how effective a light fixture is. But, obviously, a ten watt light that produces mostly infrared or ultraviolet radiation is not going to be as effective as one that produces a spectrum that mimics a 6000 K black body, and if that light is three feet above the water it isn't as effective as if it is three inches above the water. It just isn't a valid parameter for anything approaching a scientific method. Just be happy it works reasonably well for tanks in the 20-100 gallon range.

Have a butcher`s at this Graeme. Personally, i think the calculator at the bottom overestimates the light levels required.

Lighting in Amano Aquaria

Dave.

I think what Graeme is trying to understand is why the rule breaks down for smaller tanks. My first thought was that possibly the lumen to wattage ratio for fluorescent bulbs wasn't linear but actually looking at some figures for different bulb sizes this isn't the case, so rules out that theory.

I then thought about surface area and this is where I think the watt per gallon rule goes wrong. If you have a 5 gallon tank and a 50 gallon tank this equates to a volume difference of 10 fold but the surface area difference will be a lot less, possibly about a quarter depending on tank dimensions. Now doing some quick figures in my head a 50 gallon would require about four times the amount of light than a 5 gallon to achieve the same level of 'brightness'.

So calculating watts against surface area may give a more accurate representation because changing the depth of a tank greatly affects the watt per gallon figure but not the watt per surface area figure. To my way of thinking it's the amount of light on top of the tank that matters as the depth (within reason) doesn't make too much of a difference to the lighting levels

If memory serves me correctly then this has all been gone into many times before on different forums and the conclusion always seem to be that for simplicity sake it is best to stick with watts per gallon.

Hope that makes some sort of sense
James

Simply put: smaller bulbs suck.

The 13w PC lights stink ve an 18 w or a 40 watt relative to distance and micromols of light put put relative to watts.

I have 26w of 2x13 w PC lights putting out only 80 micromols at 4" and the an 18 w lamp, less watts mind, still a PC and still 4" and it puts out about 180 micromols.
The 40 watt on a tank 2x the size puts out 250.

So.............the ability for a dinky little light to produce the same amount of light per watt goes down as you reduce tank size.

Regards,
Tom Barr

So there is no real reason, it just so happens it works.
Is there a test to be done here?
There was something I read about LUX per square inch. Below 20Gal is this a much better aproach to lighting a nano?

Sould it not be more, watts to surfice area AND depth? If so, how would you figure that out.

Im just realy exploring why, I know it works, and i know how to implement it.

Thanks for the link Dave, found that a while back, still doesnt answer anything.

Cheers,
Graeme.

Thats volume!

Doh, your right!!

So there you have it. Back to the begining. How do we get the right light for nano's and pico's. Sould there be a WPG for tanks from 10gal-200gal, and then a second set for 0-10gal and 200-........gal?

Why would the WPG rule also not work for extra large tanks, whats going on with light in small and large volumes?

Graeme.

Well, the smaller bulbs have less area, thus are more light a point source, they are cheap, wimpy and have namely poor light from the electrical nodes which on a small short tube means less for the rest of the bulb.

They also have junkier reflectors as a rule.

The scale for micromols per watt is not linear.
Other issues such as finding a small enough light for a nano is also a reason.
Water mixing is also easier in a nano.
On a large tank with many bulbs, you have many different angles that light can strike the leaf, but in a very small tank close to the surface, all you have is one direction and little diffusion.

Rather than guessing the light intensity, I just use a light meter that measures micromols, they cost 249$ now for the Apogee, much less than the old days of 600-1200$ for the licor meters.

Regards,
Tom Barr