My 12 yr old son got a 40 gallon seaclear system 2 tank and a few cichlids in October. We are doing something terribly wrong though because every week the water is disgusting and we are doing 60% water changes. It is as if the filter is not filtering. The directions with this tank were terrible. Are the bio balls the filter? We have the white "prefilter" that we are rinsing weekly. Should we have carbon somewhere in this tank?? What exactly is filtering the water? Because 3 days after cleaning the tank is a cloudy mess...it seems that there must be a place to put carbon? Is this a terrible tank? I am extremely frustrated. Can anyone help me out with this?