James' explanation tells the story. The wet/dry or cannister filter do not aid in the last part of the nitrogen cycle; nitrate to nitrogen. LR
does to a certain extent and so does a DSB
. Macro algae also aids in that regard.
If you have enouhg LR
(1˝-2 pounds/gallon) you do not need a cannister or wet/dry for biological filtration. The LR
will not only convert ammnia to nitrite and nitrite to nitrate, it will also help convert some nitrate to nitrogen. In combination with a dsb
the effect can be enormous.
So the wet/dry or cannister is not really a nitrate factory so much as it is only 2/3 of the factory needed to complete the nitrogen cycle. Well maybe it is a nitrate factory then