Originally Posted by beetlebz
the same link as i posted back in this thread. The guy had too much anaerobic media and the filter was producing h2s. ill find the link tomorrow
Found it: Here's Nevin pointing to the third denitrifier that he built. This denitrifier is again contained in a 5-gallon plastic utility bucket. The water is pumped from the system into the bottom of the bucket and flows upwards through the denitrifying media. Near the top of the bucket is a threaded plastic L-fitting that screws into the bucket and connects to a piece of clear plastic tubing that returns the water to the system. This denitrifier is now working too well and removing all the nitrates, which may force some bacteria to use sulfates and produce hydrogen sulfide. When Tom inspected the system, he noticed a smell that my be partially hydrogen sulfide. The solution may be to remove some of the denitrifying media in the bucket. Incidentally, on the left in this photo is a commercial bio-wheel filter.
Tom and Nevin Bailey (I presume no relation!) also claim that we want to maintain 20-40ppm nitrates in the system. This seems curious to me since in nature, unless polluted, fresh water has little/no nitrates. I wonder why would we want 20-40ppm nitrates in out tanks when we've all heard <20ppm (lower the better) is best?
I've studied many denitrator systems and this is the only place I've seen with such a claim or caution. I am uncertain what happens with the rise and fall of nutrients and/or available nitrates. I know that hydrogen sulfide can be created in deep substrates if/when detritus gets down there, however, it's presumed that this typically does not cause harm in the aquarium. Also, in the case of this filter, since the discharge is above the aquarium water level, any gases should release before re-entering the tank.
I/we can't measure sulfides, so I don't know how we could possibly judge any media volume relativity.
I'm thinking I/we just move forward and see how it goes.
I'm hopeful I'll receive the Nitrate Remover and API filter today as it reached my local post office yesterday. I have a 15g bottled water change ready and will do that just before adding the nitrate remover product. I'll also give the filter another shot of Stability.