Stops Algae Growth Fast. No More Green Water or Algae Growth. Will Not Harm Fish or Ornamental Plants. CrystalClear Algae D-Solv is an EPA registered algaecide to control active algae blooms in self-contained aquariums, ornamental ponds and fountains without any outflow. Algae D-Solv pond and fountain algaecide is used to control green water, string or hair algae and blanketweed. Once pond algae growth is under control, weekly doses of Algae D-Solv will control algae growth and reduce pond maintenance. Algae D-Solv will not harm fish or ornamental plants when used as directed with vigorous aeration