Hello have question regarding how many powerheads to use with undergravel filter? And the best kinds. New tank set up 10 gallon to 29 gallon. I have a whisper 30 in addtion to UGF. Wanting to figure out will one powerhead be enough to be used or it has to be two? My son has had 10 gallon tank for 3 years with whisper and UGR W/airstones no cycle problems.