I change about 10% of water a week I have a wave maker on the back of the glass and two power heads on the left and right pointing down , I also have a small ext with rowa in to help but even tho I suck it out every week it is still coming back any ideas? my son says the flow is wrong .Being as he works in a fish shop I get my water checked and it comes back ok any ideas? I want to ditch the power heads and replace it with another waver maker and have two (left and right) or maybe the ones I have are not in the right place all three are at the top of the tank