Try this. The clouds are the dead algae as our friend mentioned before. Raise your CL to 5 PPM and balance out to 7.4 PH and 90 to 100 ALK. Keep the CAL at 250 to 300, and then shut off the pump for 2 days. The 5PPM of CL will keep anything from growing back. Let the cloud settle to the floor. Live algae floats, dead algae sinks. When you can see the bottom covered with the "Dead cloud", start up the pump in waste mode and vaccuum that dead algae out of the pool all together. This will result in a clean bottom and none of that Dead cloud in your pump. Then Backwash and Filter. I just finished this process on my 50,000 Gal Oval in Pensacola. LOOKS GREAT!!! As a CPO I do this all the time and have my friends do it as well. It really works.