For best results, De-nitrate should be placed to assure the flow of water through it, such as in a canister filter, chemical filtration module, or box filter. Flow rate should not exceed 200 L (50 gallons) per hour. If higher flow rates are unavoidable, use Matrix or Pond Matrix. It is best to rinse off dust before use. Once De-nitrate has been in use for several days, nitrate concentrations should start to fall and level off gradually at a concentration of about 4–5 mg/L as nitrate. As long as nitrate concentrations remain under control, the product is not exhausted. Each 500 mL of De-nitrate treats about 100–200 L (25–50 gallons), depending on initial nitrate concentration and the current biological load. Enough should be used to remove nitrate at a rate at least as fast as the rate of formation. If very high nitrates are initially present, they should be brought down to less than 20 mg/L with water changes.