Bio filtration in the freshwater aquarium.

[Juxtaroberto]

Not true. Uneaten food, old turds and rotting plant leaves contribute as well. Keep them out of your bio chamber and out of your system for best results.

Absolutely right. I completely blanked on that.

Let me rephrase: there will never be any more nitrates in the water than the total ammonia input from all conceivable sources.

However, I seem to remember reading something about another kind of bacteria within live rock being able to take up nitrate and convert it to nitrogen. This does not happen naturally in freshwater tanks, because those bacteria are anaerobic, and there's really no oxygen-free place for them to grow (unless you have super thick substrate). I read about some guy who would run his water through lots of pipes. The point was that at some point down the pipe all the oxygen would run out and then those anaerobic bacteria could grow and turn nitrates into nitrogen. I also remember reading that this is sometimes risky, because sometimes you can also produce sulfur compounds, which would kill your fish.

So, just keep up with water changes. S'all good.