We just put in a new SWG fiberglass pool, and have two issues. The first is that during construction the installers got a LOT of limestone gravel and dust in the pool. The dust settled out and aggregated and now we have about a dozen white spots on the pool bottom that are proving difficult to remove. Our PB is working on the problem. He had us add a metal chelator and then Conquer, a product that removes calcium carbonate. So far, that hasn't helped. He told us that he will have someone physically remove the spots with light grit sandpaper. Does this sound right? Any other options on how to break up and remove these deposits? Second issue is new Pentair gas heater. We keep getting AFS or AGS errors and heater quits working. I can get it to restart if I backwash and put the pump on at maximum. Pressure is never above normal when the heater faults. Any ideas on what is wrong? PB is sending tech for this problem as well. Appreciate any advice.