Snoop is good guy to listen to, he obviously knows his stuff! Ive been running 2 DWCs for the last few weeks and definitely Snoop is not joking when he says temp is the most important factor. On my 2 site DWC I run a 4 output pump that really bubbles the crap out of it. On my 4 site I use a dual outlet pump and 2 singles (just cause I had them). Both have about 8 airstones but I run 18 gallon Rubbermaid res. I figure you can never have enough bubbles. To keep my temps in check, I have to drop bottles of frozen ice into the res about every 4-5 hours depending on how hot it is. Sometimes even after 8 hours of cool night time I find my res at 73 F.

I expect specifically with tap water, but when my res tempatures get above 72F around here, you get major outbreaks of red algae. Long as it stays below that, they THRIVE!!!