My situation..

[Dudun]

I've got a 20gal Long - and plan on doing my CFL retro-fit tomorrow.

Looking at getting 4-16w bulbs, which would give me around 3.2 wpg.

Is that too much without running some sort of CO2 or ferts?

 

[kimmisc]

Yes. That's alot of light. You need some CO2, preferably pressurized, and ferts.

 

[AquaPonixRox]

well i think ya need to account for the fact that the 16w bulbs do not penetrate as far , so i would say get 2 26w or would say use all 4 16w bulbs

 

[Cory Keeper]

A 20 long, heh..... I had 3x23w CFLs over my 20 long, no ill effects. yes, I had Green Spot Algae, but that was normal. It worked out very well for me too.

And I don't think you need to worry too much about penetration, that tank is only 12" deep.

 

[gmh]

I would start with 3X16 watts. That gives you 2.4 watts per gallon spread out pretty well. Should be good for low tech planting.

 

[Blueiz]

DIY co2 will work well for a 20 gallon tank.

FWIW, I run 4x65 watts of PC lighting over my 75, which comes to be about 3.5 watts per gallon and I do not run co2 or dose ferts. I have no prob with algae whatsoever, of course the tank has been running for 3 years and is completely mature as well.