Although not normally a major problem for most fish, excess nitrate (NO3) in a reef aquarium can be very detrimental the health of corals and many other invertebrates. Aside from using a denitrator unit, a number of methods and materials can be utilized to absorb or convert nitrate to a harmless substance. Here are some nitrate absorbing products considered to be the best to help resolve high nitrate problems in saltwater aquarium and reef tank systems.
1. De-Nitrate
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Manufactured by SeaChem, De-Nitrate removes nitrates, nitrites and ammonia. This product comes in loose form and must be contained in a mesh bag or in a filter chamber and placed in the water stream. 
2. Purigen
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Purigen is a synthetic adsorbent, not a mixture of ion exchangers or adsorbents, but a unique macro-porous synthetic polymer that removes soluble and insoluble impurities from water. Purigen removes proteins, nitrites and nitrates, ammonia, and a broad spectrum of organics. Purigen darkens progressively as it exhausts, and is easily renewed by treating with household bleach.
3. Poly-Filter Pad
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With the Poly-Bio Filter Pad by Poly-Bio-Marine, Inc., water impurities like phosphate, nitrate, copper, silicate, and even ammonia are absorbed. The pads can be regenerated by simple rinsing in saltwater (saltwater use can be regenerated by the reverse, rinsing in freshwater). Simply roll or cut the pad to any shape, place it inside a canister filter or incorporate it into any type filtration system to easily remove troublesome elements in saltwater aquariums.
4. FilStar Nitra-Zorb
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A blend of natural and synthetic ion-exchange resins that selectively remove ammonia, nitrite, and nitrate. In new aquariums, Nitra-Zorb controls the level of toxic ammonia and nitrite during initial development of the biological filter. In established aquariums, it helps control sudden surges in ammonia and nitrite caused by the addition of new fish, or anytime ammonia or nitrite is detected.
