I think I understand!! So NH4 is the real culprit when it comes to algae? Unstable CO2 creates mini spikes in NH4? High light gives little room for error. Agree with primary concern should be with plants, just trying to understand the cycle. Regarding less light and good CO2 - is that basically plant related meaning it is dictated by what plants you intend to grow? I have a 65gal with 4 39W T5s with individual reflectors using three 6000K and one 6500K. My thoughts are that I could possibly reduce but my Rotalla wallichii tends to close up when one set is off. So would this mean that if I want to grow wallichii, then I need this higher level of light? Thanks Vaughn and Tom

Chip