What causes high nitrate levels in freshwater fish tanks?

Answer by  Ruby40 (372)

Many possible causes: too many fish, too much fish food, and/or a new tank. Nitrates are a natural byproduct of the breakdown of fish waste and other biological matter. An established tank (over a couple months old) will have natural bacteria that break down nitrates.

Answer by  bill14 (308)

High nitrate levels are caused by the decomposition of fish waste. If there is not adequate chemical filtration, nitrate levels will rise to high.

Answer by  jollyliza2004 (43)

High nitrate levels in freshwater fish tanks can be caused by Nitrobacters. Nitrobacters break down nitrite into nitrate. If nitrate is high, this may increase the water's PH level and may cause the build up of ammonia which is detrimental to the health of the fish.

Answer by  Requin (290)

Nitrates are the final product of the "cycle" that goes on in a freshwater tank. Nitrates levels can be lowered easily by doing a water change on your tank. To keep the levels down, you can add live plants, but you will still need to do regular water changes.