Nitrates stay high no matter the water change

[mudduck]

This is my wet dry on my 250 gallon tank I also have that huge canister I clean it once every 6-8 weeks. I change pads on wet dry weekly and I do weekly 50-75% water changes. My City water is zero nitrates out of the tap nitrites are zero in the tank ammonia is zero ph is 8.2 nitrates are high as the chart goes after 7 days from water change With this much filteration what am I missing? It’s always been this way indeed once daily no waste laying around no dead fish filter pads are always filthy like writhin a day of use .....

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Nitrates are the end result of the conversion of harmful ammonia & nitrite. Filtration does not remove nitrate, it produces it from the bioload of your tank. Fish respiration, waste production and feeding contribute to the bio load, the biologicals in your filters convert it to nitrate. The only way to (cost) effectively remove nitrate is to do large weekly water changes.
HTH. Danny