OK. thanks for all the responses. I will have to get a test kit and post results here. I was concerned that maybe for a 10,000 gallon pool that maybe the 50sq foot is too small. I asked that because even when the pool did not have Algae, i was still seeing the pressure go up every other day or so. What is the reccomended size filter for this pool? I would rather know and plan to change the filter is that was the problem - the filter not filtering enough water to keep up. Thanks