keep the powerhead on. water circulation is just as important during the day as at night, and fish do best in an environment that is not constantly changing.
my powerhead is timed to go on w/ my co2 only.
i want it to go off at night so my fish have an ease at bed time.
besided the filter is circulating water, so ther is current.
On another note, you could also feed the McDonald's to your fish and then become the first person to sue McDonald's for making your fish obese or blame their death on it. If it works for fat kids, why not fat fish?