Black Algae

Ask any pool pro about this one, and you’ll get a shudder. Black algae starts as a small black or dark green spot, and spreads rapidly around the pool. You’ll see it first near lights, jets, corners, or in the tile grout. While not impossible to remove, it requires a very different approach than green pr mustard algae.  The visible spot is actually a waxy shell that protects the plant. Just shock or algaecide won’t do anything to budge the problem. You MUST brush with a stiff brush to remove this. waxy layer so the chlorine can kill the plant. In tight areas, a pumice stone works well, or in white plaster pools, a chlorine tablet will do. In cases where there are too many plants to get by hand, use a silver-based algaecide and a large stainless steel brush to remove the coats. Use a Tri-Chlor or Di-Chlor shock to kill the plants, and keep the chlorine at the upper end of range until all discoloration is gone. Make sure you vacuum the debris out of the pool and clean your filters or backwash ASAP.