We are looking to replace our purex triton 2000 DE filter purchased in October 1999. We have had issues with green algae on the walls of the pool - chemicals are in line but we started to see DE shooting back into the pool. We have replaced the grids and just about everything on the filter we can with no success. Looking for suggestions on what filter to purchase as a replacement. Our pool is about 20,000 gallons, pebble tec, 6ft waterfall. We have 2 pumps ~ purex whisperflo 2 hp. Appreciate any suggestions.