Good lighting for small tanks with light fixtures less than 36" have been a problem. Most fixtures less than 36" to be used with no flourescents are made with white plastic reflectors. I played around with the idea of using mylar to line my cheapo reflectors. I finally went to the LFS and bought a fixture with a polished aluminun reflector and 2 HO T5 bulbs for my 20 gallon tank. I was struck by the intensity of the light. Compared to my old NO flourescents with white fixtures. The light appeared to be 2-3 times as bright even though the wpg are virtually identical. No surprise, but it did get me thinking about how to determine how much light is actually reaching my plants.The type of bulb, quality of the reflector, distance of the light from the water, cleanliness of the tank top etc. all affect the amount of light.

I like to keep small tanks in the 20 - 30 gallon range with diy co2 and 2 -2.5 wpg. I normally use 3 liters of wine yeast and sugar per 20 gallons and that seems to provide a reasonable and steady level of co2. I do EI dosing "by the book". Will my HO T5 lights of 48 watts on a 20 gallon be too much light ? Does WPG have any real meaning ?

I also have been looking at power filters and co2 loss. I always "over filter" my tanks. I use an aqua clear power filter rated for a 50 gallon tank on the 20 gallon described above. The normal recommendation is to keep water levels high to reduce co2 loss. To be honest, it appeared to me that keeping water levels very high in a tank with a larger power filter pushes the water down and forward. The forward motion causes noticable ripples. When I lowered the water level the water falls into the tank with less forward motion and surface turbulence seems less. It also appeared that for tanks larger than 20 gallons you really need to add a power head to get decent circulation if using a power filter. I don't want to mess around with a canister filter for a small tank. Maybe I'll stick a sponge on a power head. I use a drop checker, but there appears to be something wrong with it. It always measures the same level of co2 in all my tanks so I don't have any real objective data to support my obsernations.


Henry

48w of T5 is plenty on a 20 Gal.
Try running it for 9 hours.

This will slow the growth rates down some.
Regards,
Tom Barr

I have had this same experience. I'm not sure why this happens. It starts out blue, but then turns green in the tank. I never turns blue when I turn off the CO2 at night, but then again maybe the PH does not rise that much over that period.

I also wish there was a better recommendation in this hobby for lighting rather than WPG. As you said, you are getting 2-3x as much light with the same watts. Friends have asked me, "is there some converison for using CF and T5 lighting?" There must be a better way. I think this hobby needs an affordable PAR meter or something to be able to measure light intensity in their tank. Maybe we should just watch our plants, and go with what works! This sounds like a good idea, but then when the beginner goes out and buys a fixture only later to find out it is way underpowered, they then have to go and buy a new fixutre. This brings me back to the idea that some kind of conversion factor for different types of lighting would be good.

Ex-reef tank keepers tend to go way overboard on light - they buy the 200 watt fixture for a 20 gallon tank. Pure beginners do the opposite - they buy the 15 watt fixture for that 20 gallon tank. That is why I still like the watts per gallon standard.

If you shoot for about 2 watts per gallon with any fixture you are at least in the right ball park for having good lighting. Maybe you need to add 50% more light, or turn off a quarter of the light, but you rarely have to junk the fixture and buy another one.

Then I believe there is another ballpark number: T5 bulbs with individual parabolic looking reflectors are 1.3 to 1.5 times as intense as AH Supply type bulbs with AH Supply type reflectors.

And, "Power Saver" screw-in spiral wound fluorescent bulbs are probably less than half as intense as AH Supply type bulbs and AH Supply type reflectors.

I'm not at all sure where T8 or T12 bulbs fit in there.

Keeping these simple ratios in mind I think you can get close to a good light for any 20 gallon or bigger tank.

Yea, but that takes experience, something newbies lack.
Also, what yardstick does one use?
Some are very picky, some folks ain't.

As far as affordable PAR meters, apogee makes one for about 250-300$ that's submersible.

That's about as cheap as you are going to get for light.
A simple solution is for the club to buy one for folks to test and compare so the cost is not that much.

Most clubs can generate 250-300$ worth of plant sales on line or at the Fish clubs, LFS's etc.

Regards,
Tom Barr

In my case the drop checker turns yellow and stays yellow no matter which tank I put it in. I even put it in a tank with no co2 running - still yellow.

I kept a reef tank about 30 years ago. Back then you used halides or t 12 vho bulbs. Since I have been keeping plants This is the first time I have used any of the newer high intensity bulbs. My fixture has a single parabolic reflector for the 2 bulbs. I understand the WPG rule is a general guide but the difference was so striking it prompted my post. The lights look great. By the way, IMO, planted tanks are the most beautiful. However, they are for me the most difficult tank I've ever kept. No green thumb for me.

Do you have distilled with 4DKH water in your drop checker?

Yes and I double checked the kh using double the amount of water in the test vial so that each drop of reagent measured 1/2 degree.

It's strange that it won't change back. Maybe your bromothymol blue is bad. The only other thing I can think of is that the amount of air or solution in the drop checker is so large that it takes a very long time to change color. If it's a standard drop checker I can't see this being the case though. If you put it in a bucket of regular tap water does it show a different color?