We are about to purchase a Viking Claremont fiberglass pool for a new home being built in St. Croix, USVI. Our current inground cement pool has a Hayward Goldline SWG I purchased about five years ago for around $500. I am looking at another Hayward Goldline AquaTrol, but it specifies for above ground pool up to 18,000 gals. Out Claremont is less that 18,000 gals, so what is the difference in a SWG as regards above ground or inground?