Does live rock remove nitrates?

Aquattro · #1 11-21-2007, 01:14 AM

I've always believed, and my tank has always followed along with the idea that live rock, in sufficient quantity, removes NO3 from the water column. My understanding from the various articles I've read or threads I've seen posted is that the anaerobic areas within the pores of the rock convert nitrate to free nitrogen gas that is then removed via regular gas exchange at the surface of the water.
Now I noticed a comment by another experienced reefer that they didn't think this happened with rock, and after a brief discussion, I'm confused. (Yes, again).
Is it everyone's assumption that live rock performs this function or not? Any written confirmation either way that can be linked to?
I've always had 0ppm NO3 in my tank, regardless of water change schedule. I've usually had a fish load on the light side, but still. If the rock wasn't removing it, then what's going on? My assertion that NO3 was 0ppm is based on various hobbyist test kits, frm Hagen to Salifert, over a span of 6 or 7 years.

Thoughts/comments?

Voli · #2 11-21-2007, 01:18 AM

Your absolutly right about your views on Live rock, it does remove NO3 just as you have said.

marie · #3 11-21-2007, 01:39 AM

I've never had problems with NO3 and although I have no idea if its a coincidence or not, I like lots of live rock and never cared for the look of a DSB ( I have a shallow sand bed).

Aquattro · #4 11-21-2007, 01:40 AM

oh, right, sand beds. My findings are with and without a sand bed.

Delphinus · #5 11-21-2007, 02:13 AM

If it wasn't the rock, what else would it be? Well, OK, actually, I'll say that I don't think it's the rock, but my understanding has always been that the rock is a convenient "container" for the anaerobic bacterial strains that do the denitrification. Other things can shelter those species of bacteria just as well but rock is one of them. Continuing this line of reasoning, I think that some rock is better than others at harbouring bacteria than others, and, I think you can have an event which causes you to lose bacteria and thus remove or deminish a rock's ability to perform denitrification (but conversely, I think that rock can also thus be renewed).

Der_Iron_Chef · #6 11-21-2007, 02:54 AM

I concur with Tony and the others, but I'd be curious to know what one would look for in rock that is better at harboring bacteria.

Delphinus · #7 11-21-2007, 02:57 AM

I think mainly the porosity, or perhaps it's better stated as the "ratio between surface area and volume (and/or mass)".

sphelps · #8 11-21-2007, 03:31 AM

Anywhere where dissolved oxygen is depleted (anaerobic) bacteria can use nitrates instead of oxygen to respire. However in order for the process to work you need some kind of electron donor or carbon source such as methanol or ethanol. Or something like that, basically if you rock houses these anaerobic zones then denitrification could occur but not to an effective level without constant addition of a carbon source. This is why some people does vodka (ethanol).

All this theory about denitrification in the aquarium with the use of live rock and deep sand beds IMO is over rated, and I don't think much of any denitrification processes are occurring in our aquariums, in the ocean yes, but it's just not feasible in the aquarium.

reptile guy · #9 11-21-2007, 03:39 AM

Out of curiosty how do you dose vodka?

Quote:

Originally Posted by sphelps

Anywhere where dissolved oxygen is depleted (anaerobic) bacteria can use nitrates instead of oxygen to respire. However in order for the process to work you need some kind of electron donor or carbon source such as methanol or ethanol. Or something like that, basically if you rock houses these anaerobic zones then denitrification could occur but not to an effective level without constant addition of a carbon source. This is why some people does vodka (ethanol).

All this theory about denitrification in the aquarium with the use of live rock and deep sand beds IMO is over rated, and I don't think much of any denitrification processes are occurring in our aquariums, in the ocean yes, but it's just not feasible in the aquarium.

Aquattro · #10 11-21-2007, 04:46 AM

Quote:

Originally Posted by sphelps

I don't think much of any denitrification processes are occurring in our aquariums, in the ocean yes, but it's just not feasible in the aquarium.

So following along this thought, where did my nitrate go? I'm talking about long running systems never showing detectable NO3, even feeding "well" with PE mysis, daily nori, etc.

I like to believe the rock is doing it, but how does the water reach the anaerobic areas within the rock at sufficient turnover to process the entire tank?
And I'm not certain you need a carbon source with these bacteria, now you're gonna make me have to hit the books again.