NP-active pearls are a unique and natural way to control nitrate and phosphate in all aquaria. A pure, 100-percent natural bio-polymer and made in USA NP-active pearls act as both a carbon source and medium for beneficial bacteria. As the bacteria consume the NP-active pearls they remove nitrate and phosphate from the water, out-competing algae and resulting in better water quality. NP-active pearls are an easy way to remove nutrients from the water that would otherwise be available to stimulate algae growth. NP-active pearls are pure and were developed to offer several advantages over other types of bio-polymers - they are made in USA, specifically designed for use in aquatic culture systems, are ASTM d7081 certified marine biodegradable in aquatic environments and are tested for use in aquatic systems. How to use: the recommend amount of NP-active pearls is 1/4 cup per 20-gallon of aquarium water (3ml per-gallon). When first using NP-active pearls, we suggest starting with 1/3 dose or 1 ml per-gallon (1/4 cup per 60-gallon) and over a few weeks increasing the amount of NP-active pearls in your system. The rate at which additional NP-active pearls need to be added varies for each aquarium due to factors such as feeding amount, fish load etc. Generally, it is best to replenish your pearls every 6 to 9 months. NP-pearls active pearls never need to be replaced unless your reactor shuts-off and the pearls turn black and produce an offensive odor.They are best used in a reactor or similar device where the pearls are kept in constant motion. It important to maintain sufficient water flow as the bacteria consume oxygen. We do not recommend putting them in a bag and just laying the bag in the system. If clogging occurs clean the reactors and rinse the pearls before re-starting your reactor system.