> Sure it does a great job of keeping Ammonia and Nitrite down, but does
> nothing (at least that I've heard) for Nitrate.
I think there's no normal filter that does anything against Nitrate.
Nitrate can be reduced by bacteria, that are living without any oxygen!
So there are special Nitrate-filters, but they are running without any
oxygen and the bacteria have to be feed with alcohol.
Additionally I think the wet/dry filters do the best job on reducing
Ammonia and Nitrite compared with any other filter. (except the fluidized bed
filters, I don't know)
But wet/dry filters are extremely dependant on the air around them! A friend
of mine has killed all bacteria in such a long running wet/dry filter with
smoking in that room. The bacteria were killed and in the following a lot
of the fishes were killed, until he found out the reason for it.
But for the oxygen-liking bacteria, that transform the Nitrate to Nitrate,
the wet/dry filters do the best job.
Karsten