Algae problems in ponds have become one of the Koi keeper’s most common complaints. Nuisance algae usually takes on two forms; green water and filamentous algae known as blanket weed, and both appear to work in partnership to curse Koi ponds. If a pond has benefited from a UV unit which has cleared it of green water then blanket weed will proliferate, thriving in the clear sunlit pond water enriched with nutrients.

Crystal clear water is common for Koi ponds which have been treated with a UV unit, but unfortunately so is being choked with unsightly fronds of hair-like blanket weed. If, however, a pond suffers from green water, then there is little chance of blanket weed troubling the same pond. A few unfortunate ponds will suffer from both forms of nuisance algae at the same time. Having cracked the green water problem with a UV unit, the Koi keeper’s final assault on blanket weed may well involve a variety of treatments that are added to the water to solve the problem.