Water Movement

fishorbust

Member
I have a 20G Tall tank with a Maxi Jet Powerhead 400, (106gph) in the top left part of the tank aimed upwards and towards the middle of the tank. I used to have it in the middle blowing up and to the middle. After i moved it up i notice yellowing, green stuff start to form around the bottom all around the tank. I was told that when i get corals that i needed another powerhead in the other corner mirroring the one on the left. Should I stay with the Powerhead 400, Or go with something larger? Should i move the powerhead back down towards the middle of the tank?
 
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