Instructions
Change aquarium water every four weeks. When nitrate levels are too high (greater than 10 parts per million) frequent large water changes will help lower it quickly. Change 7 to 10 gallons of water every two weeks. Make sure the temperature and salinity of the new water matches the aquarium.
Install a denitrification filter. Denitrification filters are biological filters that break down nitrate. These filters use anaerobic bacteria to break down nitrate into nitrogen gas, which escapes into the atmosphere.
Dose your aquarium with an organic carbon source, such as unflavored vodka, sugar or vinegar. Start at 0.1 mL of vodka per 25 gallons. Each week, add 0.5 mL of vodka. After the second week, check the levels of nitrate and phosphates. If the levels are the same or mostly unchanged, continue adding 0.5 mL of vodka until the total reaches 1.8 mL daily.
When the levels of nitrate and phosphates drop to an undetectable level, cut the dosage in half and maintain. If the nitrate and phosphate levels begin rising again, add 0.1 mL of vodka until they begin to lower. Use this dosage as your maintenance dose.
Plant mangrove plants in your aquarium. These plants feed on organics and nitrate, and live in saltwater. Use live rock or sand, or a combination of both.
How to Lower Nitrate Levels in a Saltwater Fish Tank
High nitrate levels in saltwater aquariums cause algae blooms and adversely affect plants and fish. Nitrate is produced as waste breaks down. Waste cycles from ammonia to nitrite to nitrate. Discover why nitrate levels in your aquarium are too high before lowering it. This helps you prevent nitrate levels from rising again. Common causes are bioballs, biowheels, filter pads, foam blocks and tubes, overfeeding, undergravel filters and lack of water changes. Too many fish can cause nitrate levels to rise; there should be three inches of fish per square foot of surface area.