Haha, ya I think a Sailfin tang would be a good choice. When it gets too big to turn around I will upgrade to a 30 gallon.
Do you mean how tall is the light or what length does the fixture stretch to? When I bought the fixture in Petland I noticed some 12" T5 bulbs. Not sure if they were HO or NO though. I didn't see a fixture for them, but I didn't ask either. Maybe look into that?