Nitrates are a natural by-product of the bacterial "reduction" or removal of Ammonia and Nitrite in the natural pond's ecosystem. Nitrates are an under-estimated fish killer. When fish are sick, and the history contains some information to suggest the pond has been set up for a while, you can bet Nitrate levels are part of the problem. This is especially true for Goldfish and "flipover" disease. Once dismissed as a "non" threat to Koi and Goldfish, exceptional information exists to suggest this is not true. Scientists initially evaluating Nitrates as a toxin did not test their subjects long enough. Nitrate accumulations cause dilation of the veins in the fins and other health problems. Never let your nitrate levels exceed 100 ppm or illness and vulnerability to disease will be the result!
Nitrate control in Koi care:
1. Made from Nitrite by Nitrobacter
2. Toxic above 120 ppm (Nitrate test)
3. Signs include red streaking in fins, dilated blood vessels in fins and skin, "heavy" smelling water, and lethargic fish. Folks with fish which are "poor doing" can be rewarded to check Nitrates. Chronic illness or susceptibility to disease are often caused by high Nitrates.
4. Ideal range: 20-60 ppm is acceptable.
5. Do massive water changes to reduce levels below 80 ppm.
6. Remove by water changes. Allow algae to grow on the liner.
7. If you usea algae destroyer, you will have no plant Nitrate utilization. This can be hazardous.
8. Generally not acutely toxic unless algae are specifically excluded.