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Hi all!

I've recently noticed that when testing the water quality in my aquarium, the nitrate levels are in the danger zone. They are testing at about 80-100 ppm. I've got a 55 gallon tank filled about 2/3 with water and only one 3" RES. I have one live moss ball, as I have read that that can help to regulate the levels. Any suggestions on what I can do to lower the nitrate levels, and what might be causing them to be high? All other areas test in the safe zone, aside from the nitrates.

Thanks!!

The best answer is water changes.

Nitrates result from the RES waste. Your turtle excretes ammonia. There are nitrifying bacteria in your filter and most other surfaces that convert that ammonia to nitrite. There's another type of bacteria that converts that nitrite to nitrate.

Unfortunately, providing a safe environment for bacteria that convert the nitrate is not going to work well in a freshwater aquarium. It requires low oxygen conditions, which is also what a bacteria that produces hydrogen sulfide needs.

Plants, like a moss ball, will use the nitrates as food, but moss balls are very slow growing, so they don't use much. Most other plants will be eaten by your turtle. So lowering the nitrate requires water changes.

Besides, there are other trace minerals in the water that are used by your turtle, so the water changes replace that. Not to mention, there are other bad things that can build up in the water that don't evaporate or get bound by the activated carbon in your filter. If you are just topping off, these can build to dangerous levels.

Make sure you have recently changed carbon in your filter before doing a water change or that you treat for chlorine/chloramines. Otherwise those chemicals could kill off your nitrifying bacteria.

If you google "aquarium nitrogen cycle," you'll find much more info on this.