Hydra Silt-Less Bio Bacteria (Part-2) used in conjunction with Hydra Silt-Less Base (Part-1) reduces organic silt and sludge build-up up to 9 inches (23cm) over a 12 month period Effective mix of micro-organisms, trace elements and enzymes to digest organic silt Removing organic silt increases oxygen levels for better fish health Lake sludge digester bacteria acts fast to re-balance the lake ecology Use in Spring & Autumn for Optimum Results Shelf life 3 years, 1 kilo treats up to 400m? (1/10 acre)