Mine do great. You have to remember, I have 10 watts over 2.5 gal. That's about 4 watts per gallon. My tank is 1/4 the size of yours and not as deep so the light doesn't have too far to go. 20 watts over 8 gal is 2.5 watts per gallon. I don't know what you should have for 8 gal. Maybe someone who knows more about lighting could chime in. = )
Do you have pics of your tank?
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