Can nitrates in water kill fish?

Answer 1

Yes it can and readily does in high doses.

I recomend that you buy a water kit from your local pet shop and use it on your tank. Generally if the nitrate meter reads above 5 your fish are in trouble and may die soon.

Answer 2

Nitrates are from ammonia that get converted into nitrites by the "good bacteria" which later again get converted into nitrates by the "good bacteria". A high level of nitrates in your water indicates the build up of fish waste and the decay of live plants if you have them. It also can lead to your fish getting diseases and can cause "algae bloom". Algae bloom is when everything in your tank is going well and suddenly it is covered in algae. This is caused by the high nitrate level and means you need to do water changes more frequently.

Answer 3

Nitrate (NO3) is the final stage in the nitrification process - the breakdown of ammonia by bacteria. Nitrate on its own isn't usually harmful to fish - studies have shown that most fish can tolerate levels in excess of 100 parts per million. However, nitrate is a good guide to how much general muck is in your water - other waste products that are not tested for specifically, but build up at a similar rate to nitrate. Nitrate levels of more than 60 parts per million probably indicate that maintenance is too infrequent, not enough water is being changed, or the tank is overstocked.

Also, some species (most marine fish, some tetras, all rainbowfish and most dwarf cichlids) are very sensitive to nitrate; if the nitrate level in their aquarium rises much above 20ppm, they start to lose condition.

If the nitrate level is too high (60ppm+ for a freshwater community, 20ppm+ for sensitive Freshwater Fish, 5-10ppm+ for marines), it probably means that you aren't changing enough of your water, or that you're doing water changes too infrequently. A water change will bring the nitrates down, but in the long term you'll need to either reduce the number of fish, or increase the amount of maintenance. In a marine tank, you also have the option of trying to kickstart the process of denitrification. This can be done with certain live rock configurations, or with a special denitrification filter.

You should also remember that the nitrate tests used to check aquarium nitrate levels are not particularly accurate; it is more usual for them to give a false high reading than a false low reading. They are better interpreted as a guide than a definitive value.

Answer 4

Nitrate, NO3, is the end product of the breakdown of ammonia by bacteria. In a healthy freshwater tank that is not overstocked, a small amount of nitrate is not harmful to fish. In fact, studies have shown that most fish can tolerate nitrate levels in excess of 100 parts per million. However, nitrate is also used as an indicator of the general accumulation of muck in the water - other waste products that are not tested for specifically, but build up at a similar rate to nitrate. If your nitrate level is frequently higher than 60 parts per million, it probably means that your tank maintenance needs to be done more frequently, or more of the water changed each time. Also, some fish species (including most marine fish, some tetras, all rainbowfish and most dwarf cichlids) do not tolerate nitrate well; they may lose colour, stop breeding and generally lose condition if the nitrate level in their tank rises above about 20 parts per million. If you want to keep these species, you need to avoid overstocking and keep right on top of your maintenance.