It’s never a good sign when you have foam in your fiberglass swimming pool. It usually means the chemical balance is off in your water. Pool foam should be addressed at the source. Correct the source of the problem and the foam will go away. 

Avoid using defoamers. They are simply lipstick and cover up the problem. Go to the source. Algaecides, if overused can cause fiberglass pool and spa foam.  Also a leak in a return line can suck bubbles into the pump system which will cause foam problems.