To prevent high nitrate levels, the underlying cause of “Old Tank Syndrome,” you will need to perform regular maintenance and water changes. If you ignore this care, your nitrate will rise, and your fish will suffer.
Jan 21, 2013 - How to remove nitrate from the aquarium
I'll approach it from a bacterial and fish-health stance. Nitrite can suffocate your fish, therefore you really don't want it in your tank. There are bacteria that oxidize nitrite, but this process isn't particularly favorable in terms of energetics. This is why, when you're cycling the tank, it takes a lot longer for your nitrites to drop than your ammonia levels. These are opportunistic lil buggers tho, and still get by oxidizing to . Nitrate () is not as toxic to your fish...but we really don't want to leave a ton of it in the tank either...not only does it stress fish, but once again, clever little bacteria will jump on that opporunity. There are bacteria that, when they can't find anything else worthwhile to munch on, they'll reduce right back to ...which is really kinda counterproductive!
High nitrate can cause severe algae outbreaks and green water
In summary, ammonia is lethal, and we should aim for zero levels at all times. Sublethal levels can also go unnoticed, causing tropical fish stress and making them more susceptible to disease. If an ammonia spike does occur, it is likely to be in either a new aquarium (new tank syndrome) or due to an acute catastrophic event (overfeeding, fish death, etc.). However, rapid intervention and a mature filter will address both the problem and enable your aquarium (and tropical fish) to recover. Fortunately, a filter will reprocess ammonia relatively into nitrite. Unfortunately, nitrite is still lethal to freshwater and and proves to be more persistent and is a more stubborn problem to resolve — but that’s another story!
Are nitrates harmful for my aquarium? | Algone