POND BLOCK 4/PK JUNGLE: POND BLOCK 4/PK $9.25 SKU: JUNPB0604 QTY: Click here to save 5% off of your order! POND BLOCK 4/PK Helps Control Algae Growth in Ornamental Fish Ponds 4 blocks treats 1000 gallons Offers an easy, effective way to control and prevent the growth of algae. Leaves pond water . Helps keep pond clear from algae when used regularly. Pond block is not recommended for lilies or hyacinths. Details: Replace when fully dissolved (usually after 30 days). For best results, place the block in an area of the pond that is calm. Not recommended for Water Lilies and Hyacinths.