I have a 90 gallon tank that I'm trying.get figured out. I don't think I have enough power heads, because I've got lots of green algae growing on my live rock. I only have one power head and the LR where the powerhead is blowing is clean and has no algea. I have no idea what "size" the power head is but it's about 2 1/2" round. Do I need more Powerheads?