We had a friend give us a used 18ft x 48" intex pool. The problem was it had 2" of water in it when we went to get it, and was full of leaves and muck. We took it apart, brought it home and cleaned it as best as we could. We got up and running, and now have a mustard algae problem I can't get rid of. I have upgraded the pump to 1-1/2 hp and even replaced the sand in the filter twice. HELP??!!