I'll probably get yelled at or saying this, but I wish people would stop using the term
nitrate factory as if it's a bad thing. It's NOT. Of course bioballs are nitrate factories....they're supposed to be. Biowheels also should be nitrate factories if they're doing their jobs.
Both of these forms of biological filtrations are aerobic filters -- they both use highly oxygenated environments with massive surface areas ( the folds in the biowheels, the convoluted folds and spikes of the bioballs) to encourage aerobic bacterial growth. The aerobic bacterias such as nirosomonas and nitrospira convert Ammonia into Nitrite, and Nitrite into Nitrate. That is all they are supposed to do.
When a person says that "Oh, filter X is a nitrate factory," doesn't that mean that the filter is working? Neither of these filters were designed to remove nitrate.
Nitrate removal can be facilitated in three ways. Manual removal via water changes is the first, most obvious and most difficult way to do it (IMO of course). It's time consuming and requires major water changes, but it works.
Another manual removal technique involves cultivation of macro algae. Regardless if it's a turf scrubber or Chaeto/Caulerpa in a sump, any of these algaes will take up good amounts of nitrates for use in their cells. The key to this form of nitrate removal is the diligent removal of excess algae by harvesting your algae weekly. Allowing it to grow back means more nitrate removal for your tank.
The third way I know of to remove nitrates is to cultivate anaerobic bacteria. This is done with a deep sand bed, a plenum, or large amounts of live rock. The anaerobic bacteria in the low-oxygen environments I just mentioned will convert Nitrate into nitrogen to be released as a gas.
The fourth way (Four -- there are FOUR ways to remove nitrates. No One expects the Spanish Inquisition!!)
The fourth way is of course a Nitrate reactor, where you are deliberately creating a low-oxygen environment for the nitrate loving bacteria.
But we already know all this, don't we? So why do people say that a filter is a "nitrate factory?" Just deal with the nitrates and be happy your filter is doing such a good job sucking up Ammonia and Nitrites!
OK. Stepping off my soapbox now. Feel free to bash wherever appropriate.
