Nitrate Management in Freshwater Aquariums

Freshwater Aquarium

The importance of nitrate in the aquarium is perhaps less well known by aquarium keepers than the effects of ammonia and nitrite. Although nitrate is not as dangerous as ammonia or nitrite, large levels of nitrate have a long-term harmful influence on fish and the aquarium environment.

Where Does Nitrate Come From?

Nitrate is a by-product of nitrite oxidation in the nitrogen cycle's latter phases, and it's found in all aquariums to some extent. Increased nitrate levels are caused by detritus, decomposing plant material, filthy filters, overfeeding, and overstocking the aquarium.

Furthermore, the tap water used to fill the aquarium might contain nitrate. Nitrate levels in drinking water in the United States can reach 40 parts per million (ppm). Test your water supply for nitrate before adding it to your aquarium to see if the levels are exceptionally high. If your nitrate level is more than 10 ppm, look for nitrate-free water sources.

Desired Level

Nitrate levels in water are typically much below 5 parts per million in nature. Nitrate levels in freshwater aquariums should be kept below 50 parts per million at all times, preferably below 25. Keep nitrate levels below 10 ppm if you're breeding fish or fighting algal development.

Effect on Fish

By the time nitrate levels reach 100 ppm, fish will be affected, especially if the levels continue. Fish are more susceptible to illness as a result of the stress, and their capacity to reproduce is hampered.

Nitrate levels beyond a certain threshold are particularly detrimental to fry and young fish, affecting their development. Furthermore, the same circumstances that create high nitrate levels frequently result in low oxygen levels, further stressing the fish.

Nitrate and Algae

Nitrate levels as low as 10 ppm will stimulate algae development, and elevated nitrate is a substantial contributor to unwanted algal growth. Increased nitrate levels are the most prevalent cause of algal blooms in newly set-up tanks.

Despite the fact that consume nitrate, if nitrate levels rise faster than they can be used, the themselves can become covered with algae, resulting in asphyxiation and death.

How to Reduce Nitrate

The bacteria that remove nitrate avoid oxygen-rich conditions, unlike the aerobic bacteria that convert ammonia to nitrite and finally nitrite to nitrate. As a result, typical filters that are well-oxygenated will not host the bacteria that remove nitrate.

However, there are some steps you can take to keep nitrate low.

  • Keep the aquarium clean: Waste ultimately produces nitrate; cleaner tanks produce less nitrate that must be removed by water changes.
  • Feeding amounts: Overfeeding is a significant contributor to excess nitrate and other undesirable wastes, such as phosphate.
  • Water changes: Performing regular with water that has little or no nitrate will lower the overall nitrate level in the aquarium. If your local tap or well water is high in nitrate, using deionized water (DI) or reverse osmosis water (RO) can help keep nitrate levels low when doing a water change. However, since these are devoid of minerals, the hardness, alkalinity, and pH of the water can become too low and mineral supplements may need to be added. Mix your nitrate-containing tap water with DI or RO water to make a blend with the correct water parameters.
  • Keeping live plants: utilize nitrate and will help keep the levels lower.

Although specific filters called denitrators exist to remove nitrate, they are often more costly than ordinary filtering units. You may buy a nitrate-lowering media to put in your existing filter instead of spending money on an expensive denitrator or custom filter. These will remove the nitrate from the solution and will need to be refilled on a regular basis.