Kasco Marine Time Release 6 lb Muck Block - Lake & Pond Sludge Silt Muck Odor Remover Eliminator 6lb block - Treats up to 2.5 acre-feet of water - All natural - Safe for wildlife - Helps to reduce and remove nitrates and phosphates from the water - Removes & controls fish waste, Muck, Sludge, Silt Odors When placed in areas of water current or in feeder streams, the water movement will carry the muck-busting bacteria throughout the pond, making applications and treatments a breeze block is formulated to slowly release bacteria dosages that will treat up to 2 acre feet of water 1 step maintenance program - Each Macro-ZymeTM Time Release Muck Block is sold individually in a water tight bag, packaged in a user-friendly box - Each Muck Block is packed with high counts of bacteria CFU's, which will gradually release into the water system to aggressively attack and decompose muck and organic matter