A 20H tank is 24 inches long and about 17 inches high, so the light will be about 15 inches from the substrate if it sits on top of the tank. That Odyssea light will give you too much light unless you hang it 5-10 inches above the top of the tank. A Coralife T5HO or FishNeedIt T5HO light would work much better.
So the Odyssea light is out: too much light and I just read some no-so-good reviews online. The Corallife and FishNeedIt seem a little out of my price range (I'm so cheap! :P) but ill definitely keep them in mine! I'm trying to figure out if the Deep Blue would work? It says it takes 1 14W T5HE... Is that the same as HO? If so that would be fine from what I understand? The reflectors seem pretty decent as well from my limited judgement.
EDIT: just read that t5he=t5no so therefore the deep blue fixture would result in a very similar lighting to the single t8 I currently have. This lighting stuff... haha
Last edited by TFish5; 10-10-2012 at 12:50 AM.