Here's a description I found for some bio media I was looking at:

"A highly porous media designed to provide exceptionally efficient biofiltration for single site removal of ammonia, nitrite, and nitrate from freshwater, marine, and reef aquaria. Each liter of Matrix provides over 160,000 cm2 (170 sq. ft.) of surface, equivalent to over 40 L (10 gallons) of typical plastic ball media.
Use 500 mL of Matrix for each 200 L (50 gallons) of water. Matrix may be placed in any kind of filter, and is particularly effective in a canister filter. Matrix is sufficiently large that no filter bag should be required for most applications. Matrix works well in drip tray systems, but you may find that the larger Pond Matrix (sold separately) is better suited for such applications.

Product highlights:

Aerobic bacteria grow on the pitted external surfaces of Matrix and convert ammonia to nitrite and nitrite to nitrate.
The pores which cover Matrix are home to anaerobic bacteria.
Anaerobic bacteria convert nitrate into nitrogen gas, which is then expelled at the tank surface."

I haven't really read anything on this website (or other websites) about nitrate being converted to nitrogen gas, which I'm sure could happen, but is that really a chemical reaction we can count on to occur in aquarium situations? I mean, I would LOVE to have an aquarium that needs no water changes, but I'm sure that's not going to happen anytime soon.

What do you guys think?

Nonsense!! While this could happen theoretically, it won't amount to anything meaningful or measurable in the context of an aquarium with its nitrogen load. Here's why - the "anaerobic" layer is literally microscopic and won't hold any meaningful biomass. To promote denitrification, you would need to have a large anaerobic zone (very bad in an aquarium, would smell, fish would die). Some sewage treatment plants are being upgraded to provide denitrification, since nitrogen in our waterways promotes excessive algae growth, etc. To do this whole anaerobic chambers need to be constructed (very large) which are entirely anaerobic. Sometimes a supplemental carbon source needs to be added to that the anaerobic bacteria have something to "chew" on. They get their oxygen from nitrate (NO3) and the residual nitrogen is converted to nitrogen gas which is vented.

The manufacturer got this idea from traditional trickling filter plants (like our wet/dry filters). There, slimes would build up on the media (rock). When it reached a certain thickness (pretty thick, you don't want this in your tank), it was noticed that an anaerobic layer would form between the slime and the rock, form gas, and eventually slough the slime off. Again, this isn't very significant and you don't want these conditions in your tank.

Forget denitrification. Nice idea but not practical. Think water changes in aquaria.

Dennis

Actually there r some water chemical that can make the nitrate evap~

I see Dennis' main point though: NOT A SIGNIFICANT SOURCE OF GOODNESS. Hehe, I guess water changes are going to have to keep going.

Personally I want to keep as much extra chemicals away from my tanks as possible. I find that it's less stress on the fish and they seem happier without swimming through a giant chemistry experiment.



I might buy the product anyway, it's basically a jug of lava rocks and it's only a couple bucks.