Best light for 20L NPT?

First, as you probably noticed, the special "plant bulbs" are not as bright as other bulbs. The FloraSun puts out way less photosynthetic radiation than the T5HO UltraSun. As you found out, T5HO is way too much for the shallow 20L tank. I would think the T8 would be plenty! I use two CFL bulbs on my 20L, it's covered with frogbit and duckweed, and my Swords, Cabomba, and other plants do very well, although they grow slowly.

Did you use "Daylight" bulbs or "soft white"? That can make a huge difference in the spectrum of light. I would expect a T8 Daylight bulb would be just what you needed. Perhaps it's not the light, but your plant selection (stems?) or some other parameter?

I want to make sure I understand what you have...a 20 Long is 30 inches in length (but shallow). Was/is the T8 single tube a 24-inch tube? If yes, and you use a good tube, this is more than sufficient. I have a 24-inch T8 over my 29g which is 30 inches long but much deeper.

As for tubes, the ZooMed UltraSun T8 should be fine. Assuming it is 24-inches.

Byron.

Yeah, a 20L is only 12" deep, and 30" long. I have a T5 HO that works wonders on my 46 bowfront and just assumed that a matching length would be great on this. Clearly it's too much and I wasted my money, though. :-/

I did love the way my betta girls looked under the T5, but I will try this for a while and see how it goes.

Thanks!