Ah, ok. I was confused by the wording (and it was late).I Ordered a T8, But was shipped a T5. So I'm exchanging the t5 for the T8.
Then I saw his post after I had exchanged the T5 for the T8 that he had first suggested.
I agree, if it's a single bulb fixture...that's about the lowest light you can get over a 20 long and still keep a few, almost exclusively, non-stem plants. I don't normally advocate increasing lighting unless absolutely necessary, but you've only got enough to really keep java fern, Anubias, etc. alive. Don't expect a whole lot of growth.I've got nothing against T8, but why the T8 must have?? A T8 fixture for a 20L is about as low light as you can get. You're talking a ~17watt, 24" tube. This may be fine for Java Fern and Anubia, given the right color/temp range of the tube, but you'll need patience of a Saint. Just as an example, I've got ~20watts worth of ~6500K CFL over my planted 10g. It's literally taken 2yrs for the java fern and anubia to fill-out the tank.