[Morm]

This is what i have with 4X T5HO 39W 6,700' on a 40R. Heavy plants + CO2

http://www.marineandreef.com/Nova_SunDial_T5_Current_USA_p/rcu01152.htm

My question is this too much light? Should I /could I switch to 21W T5 bulbs instead?

 

[FSM]

Are you having problems with it?

 

[Hoppy]

Theoretically it is way too much light, but if it is working for you, why change? If you wanted to reduce the light you could probably leave two bulbs off, or, for sure, you could raise the fixture a few inches above the tank.

 

[Morm]

Do you think that 4X21W bulbs would be better than the 4X39?
3.9 Watts per gallon or 2.1 Watts per gallon.
I get a decent amount of spot algae on the glass and tons of green water when i first started, but everything else seems to be OK now.

 

[JennaH]

it depends on how far above the water the 4x39 watt fixture is. if it is mounted right on top, i would think that would be too much, but maybe hung 12" above it might not be. if you have been using it without any issues i would just stick with it

 

[FSM]

You seem to think it is bad just because it is supposed to be bad. If you're algae problems are gone, why change anything?