Does live rock remove nitrates?
 

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?

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

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).

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

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).

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.

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

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.

Out of curiosty how do you dose vodka?

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.:)

I believe the rule of thumb is 1ml per 100 gallons.

I'll pose a corollary question then, why do other long running systems, when even feeding "lightly" and lightly stocked, always show trace amount of nitrates (namely my tanks ... or in some cases, show ridiculous amounts of nitrates)?

I'll say one thing about carbon dosing though, 3 weeks of "Polyp Laps Reef-resh" has done what a year of running sulfur could not, and for the first time in well over a year I have sub-10 nitrate readings in my ritteri tank. Wish I knew what the difference was with this tank and its resistance/resilience to denitrification... it's really weird.

Well LR must do something as I'm BB and test usually 0.0 or 0.2 NO3 (or got a bum Salifert testkit).

Tony, does your theory about different rock perhaps come into play here? Maybe your rock is not porous enough?

And I believe this is typical of many (most?) tanks. Isn't it?

I beleive it is fairly typical... except for perhaps in more heavily fed tanks at least...

Yeah, I'm wondering about porosity. It's funny that you started this thread because I was basically wondering the same things and the thought had occured to me just today about the rock density.

Well, I've gone through bouts where I've fed really heavy, no change in NO3. Maybe I'm just lucky?

I guess I bring this up now after that comment I saw, and the fact I need to buy new rock in th enext few weeks.

Nitrate is removed with water changes but more importantly organics are removed before they break down into nitrates with a good skimmer. Also a refugium can work fairly well at removing nitrates. I really doubt your rock is doing very much, maybe some but very little.

If you're looking for some good information on the subject try researching waste water treatment, denitrification is a necessary part of this. There's not a whole lot out there for info regarding this in the aquarium.

ok, but after 2 months of no water changes, no refugium and a reasonably decent skimmer, still no detectable NO3.
Does anyone have a comparable FO tank where this happens? I gotta believe the rock is doing more than you think, granted perhaps less than I think. Tony has lots of rocks and a self proclaimed NO3 problem, so whati s different? He skims, changes water, etc, probably more than I do.

Let's keep the opinions coming.....

And how often would you dose that and is that what you do with your tank? Would be an interesting experiment even though my nitrates so far have always been low

Hmm, I'm actually a factory trained water quality technician, however wastewater treatment and natural denitrification in live rock are two different environments. The books I mentioned above though, are wastewater management related. As soon as I dig them out, I'll start reading. Limnology will also give us some clues about natural anaerobic/anoxic zones, so those books need to come out too. Maybe I shoulda just bought some rock and shut up :)

not done reading this yet, but so far looks like an interesting article from Dr. Ron

http://reefkeeping.com/issues/2004-0...ture/index.php

I remember hearing someone saying about dosing your tank with sugar but don't know how effective that would actually be or if that would work along the same lines as vodka. Rather use the vodka to get me drunk and not my fishes:mrgreen:

yes please
 

yes if you don't mind so your tank will get set up faster and you know what fish can make it to your new tank. :razz:

dosing vodka
 

be very careful with dosing vodka. it can crash your tank very quickly by providing too much nutrient to a certain strain of bacteria which will then start covering your rocks with slimey bacteria.

Zactly why I'm getting this going!!! :)

So this seems to answer some of the questions, while posing some new ones. Coraline growth and population of creatures within the rock can influence filtration capacity. Hmm. Tony, review the parts about "good rock" vs. "bad rock"....

Well don't know if I would actually go through with it cause so far everything in my tank is looking good and don't have much in the way of nitrates but always interesting to hear some of the different things people have tried and the reasons why


QUOTE=Chin_Lee;282682]be very careful with dosing vodka. it can crash your tank very quickly by providing too much nutrient to a certain strain of bacteria which will then start covering your rocks with slimey bacteria.[/quote]

Seems to make sense if the rock became encrusted with corals or coralline would have an effect.

Yes, and my question about how the water gets through the rock is answered with fauna living inside the rock. Lots of worms, etc, lots of movement with subsequent filtration happening. No worms, no filtration....hmm

Brad thanks for a great thread.

Following your thought above. I started to think about this. There are so many places we now get LR from. A lot is farmed line stone. Other Rock is from a dead or deep reef. I'm wondering if the good porous stuff is becoming harder and hard to find.
I have already been hitting the books but have not hit on the article that started my understanding that LR alone does not complete the nitrogen cycle. In a closed reef system.

OK so I wasn't able to dig up anything concrete yet. But I'll be back into the books tomorrow.

J

Jason, did you read that link? Ron and Eric are supposedly doing further research, so depending on when that link was done, they may have completed it by now. Maybe I'll try to ask one of them if they have more info.

The last few shipments of live rock I bought were crap. Jakarta maybe? I can't remember. All I know is my first tanks with premium fiji were awesome, before I discovered good skimmers even..:lol:

do you see any difference inNO3 with it's use? Or is it combined in existing setups?

Reading now :)

Don't have them anymore Brad, and never had algae enough to want to measure. The tanks I mention were 100% fiji premium.

All I know is that is my rock of choice.

Ya, I never went wrong with the fiji. The jakarta I see now looks like it came from someone's garden.

Well, good article but it appears Dr. Ron and Borneman had a simpilar decusion and had the resources to find the answer.

Things I found interesting
Quotes for Live Rock As A Biological Filter: Hit or MythBy Dr. Ron Shimek

Finally, the interior of the rock has to provide the appropriate physical environment, primarily slow water flow and low oxygen concentrations, to facilitate the appropriate bacterial processes.
Low Oxygen will not create a anaerobic environment. No oxygen does. therefore the anaerobic bacteria will not thrive and Nitrate will not be converted to Nitrogen gas. So is this article about Ammonia -> Nitrite -> Nitrate. Or is it about complete conversion.

I anticipated a reference to the components to the complete nitrogen cycle but never found it.

J

No, no O2 is anoxic, low O2 will creat anaerobic. For our purposes, my understanding of the article says this is sufficient within "good rock". Additionally, if you google "denitrification in live rock" you'll get lots of hits to articles that claim"oh ya, lr does do that, although without anything to back it up.