I am struggling with my pebbletec-style pool. I was away for a few weeks and it has gotten away from me. The water is balanced and tests find, but there is a buildup of green/black algae on the floor. It brushes of easily, buy my Dolphin robotic cleaner doesn't pick it up effectively. I'm thinking my first step is to vacuum it out. Can someone recommend a vacuum head attachment- maybe one with a brush attached- I can use to start getting it cleaned out?