Do they kill blackspot algae?
Yes, POOL BLOCKS and POOL DROPS Plus are one of the few effective treatments against blackspot algae which is common in all types of swimming pools. Chlorine has no effect at all on blackspot algae as only a specific long term algicide destroys the algae cells. Some scrubbing is helpful during treatment to remove the waxy protective coating that forms on the exterior of the blackspots. Tough, wall based algae such as blackspot grows slowly and dies slowly and a full three month treatment period is required to kill all living cells and this is why short term algicides so often fail. Once the algae is dead, only the mineral remnants of the spot remain and this is mostly composed of calcium and can either be scrubbed off with a stiff bristled brush or a follow-up acid treatment with citric acid can be used to breakdown the dead remnants left behind. This follow-up treatment involves lowering the pH of the pool water with citric acid (which dissolves organic marks) and sometimes some addit
