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View Full Version : Does live rock remove nitrates?


Aquattro
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
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
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
11-21-2007, 01:40 AM
oh, right, sand beds. My findings are with and without a sand bed.

Delphinus
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
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
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
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
11-21-2007, 03:39 AM
Out of curiosty how do you dose vodka?



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
11-21-2007, 04:46 AM
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.:)

sphelps
11-21-2007, 04:50 AM
Out of curiosty how do you dose vodka?

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

Delphinus
11-21-2007, 04:51 AM
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.

mark
11-21-2007, 04:52 AM
Well LR must do something as I'm BB and test usually 0.0 or 0.2 NO3 (or got a bum Salifert testkit).

Aquattro
11-21-2007, 04:53 AM
Tony, does your theory about different rock perhaps come into play here? Maybe your rock is not porous enough?

Aquattro
11-21-2007, 04:54 AM
Well LR must do something as I'm BB and test usually 0.0 or 0.2 NO3 (or got a bum Salifert testkit).


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

Delphinus
11-21-2007, 04:57 AM
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.

Aquattro
11-21-2007, 04:59 AM
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.

sphelps
11-21-2007, 05:00 AM
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.:)

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.

sphelps
11-21-2007, 05:09 AM
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.

Aquattro
11-21-2007, 05:09 AM
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.....

reptile guy
11-21-2007, 05:11 AM
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

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

Aquattro
11-21-2007, 05:12 AM
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.


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 :)

Aquattro
11-21-2007, 05:18 AM
not done reading this yet, but so far looks like an interesting article from Dr. Ron

http://reefkeeping.com/issues/2004-05/rs/feature/index.php

reptile guy
11-21-2007, 05:19 AM
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:

Chin_Lee
11-21-2007, 05:20 AM
Maybe I shoulda just bought some rock and shut up :)
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:

Chin_Lee
11-21-2007, 05:22 AM
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:

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.

Aquattro
11-21-2007, 05:26 AM
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:

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

Aquattro
11-21-2007, 05:27 AM
not done reading this yet, but so far looks like an interesting article from Dr. Ron

http://reefkeeping.com/issues/2004-05/rs/feature/index.php


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"....

reptile guy
11-21-2007, 05:30 AM
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]

mark
11-21-2007, 05:32 AM
Seems to make sense if the rock became encrusted with corals or coralline would have an effect.

Aquattro
11-21-2007, 05:35 AM
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

Jason McK
11-21-2007, 05:35 AM
Tony, does your theory about different rock perhaps come into play here? Maybe your rock is not porous enough?


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

Aquattro
11-21-2007, 05:38 AM
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.

EmilyB
11-21-2007, 05:39 AM
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:

Aquattro
11-21-2007, 05:40 AM
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?

Jason McK
11-21-2007, 05:40 AM
Reading now :)

EmilyB
11-21-2007, 05:42 AM
do you see any difference inNO3 with it's use? Or is it combined in existing setups?

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.

Aquattro
11-21-2007, 05:44 AM
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.

Jason McK
11-21-2007, 05:57 AM
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

Aquattro
11-21-2007, 06:03 AM
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.

Aquattro
11-21-2007, 06:06 AM
No, no O2 is anoxic, low O2 will creat anaerobic.

well, not on an exam, but let's use this difference for this discussion...

Delphinus
11-21-2007, 06:14 AM
Interesting article. One thing I take away from it is that the process of "cooking" rock may be a good thing to do every few years.

Jason McK
11-21-2007, 06:17 AM
Sounds good. I'll read up tomorrow and be back :)

J

sphelps
11-21-2007, 01:50 PM
Dr. Rons article although a good read, when it comes to the denitrification it's all based on too many assumptions, how do you create the perfect velocity through live rock? Where do you find rock with a uniform porosity? Way too many things have to happen for this to work.

"it is possible that dissolved materials such as the various chemicals constituting the denitrification cycle do diffuse into and out of live rock; however, it is unlikely that such diffusion moves any significant amount of materials."

Seriously I think the algae growing on your rock is removing more nitrates than your rock along.
For those maintaining zero nitrates without a skimmer, what kind of tests kits are you using?

sphelps
11-21-2007, 01:57 PM
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

Daily, it would be better if you could find pure ethanol, but vodka is probably the next best thing. I've never heard of any problems using this method, just watch for new bacteria films, if a film begins to form somewhere is it's a sing of overdosing so cut the dosage down.

It's also better if you can create a low oxygen zone and dose directly into it. A coil dinitrifier can work well for this, these have a bad reputation but they do work but you have to dose the carbon source into them and you need to achieve the proper flowrate.

sphelps
11-21-2007, 02:00 PM
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.


Actually I believe the difference is anoxic simply means no oxygen as stated but anaerobic means without oxygen and refers more to organisms living without oxygen or replacing oxygen.

Doug
11-21-2007, 02:35 PM
I would agree rock does de-nitrify but certainly not the most efficient like a dsb or plenum system. Or my turf scrubber. :smile:

I have seen pics of tanks with very old rock and doing fine. I get the same algae growth on newer expensive Fiji, as my 17yr. old Florida type rock.

How the heck does one take the rock from a full blown reef and cook it. I once also said in regards to rock being changed out after some time, that when I start throwing away rock thats $5 to $10 a pound, that the day I take up another hobby. :lol:

Reefer Rob
11-21-2007, 04:09 PM
I've always thought that algae plays a more important roll in denitrification than it's given credit for. When I switched from PCs to T5s my nitrates went from 20 to 10, and when I took a DSB refugium with too low of a flow off line it went to near 0. I'm thinking the biomass of algae living inside live rock and sand would be equal to or greater that that of bacteria. Perhaps buying or making rock with an open porous structure is more important for the growth of algae rather than bacteria, allowing light to get farther into the rock.


For anyone considering carbon dosing to increase bacteria efficiency, sugar will work as well as any of the commercial probiotic systems, but the down side is it doesn't come with an instruction manual. If you're not willing to spend a couple of weeks researching it before you give it a try, it's far safer to stick with Zeovit, Polyp Lab etc. which has a dosing regimen already established for you.

kwirky
11-21-2007, 09:53 PM
sorry for the long read!

I read a non-reef oriented scientific paper once on denitrification and how they perform it in water treatment plants. It's very difficult because there are about 100 strains of bacteria that nitrify and denitrify. Some bacteria convert nitrates back to nitrites, some to nitrogen. The study found that finding the "right" bacteria was difficult and they managed to cultivate the "right" bacteria through collecting soil samples from around the world. (On a side note, that article was talking mainly about an interesting study of using organic cotton as a carbon source for denitrifying bacteria instead of traditional sulphur; they were early yet surprisingly positive results)

Now to our aquariums. Natural "filtration" methods are extremely complex. There was an advanced aquarist article on natural deep sand beds where they tested them with livestock and without. The tests with livestock were VERY unpredictable. I think that can correlate to everyone's experiences with denitrification in their tanks. Some people say it happens, some it doesn't, probably because of the great variance in our liverock and the animals (including microscopic) we have in our systems.

Now going to bacterial products like reef-fresh and zeovit:

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.

I've noticed some interesting results very quickly with zeovit too. 2 days ago my tank was at 5ppm nitrate (salifert kit). I did a 10% water change that day. Tested today (2 days later) and it's at 2.5ppm. I know those are VERY short term results but it makes me VERY excited about the potential of the system.

I think that these bacterial products are doing a good job at taking the organic compounds (phosphate, ammonia, nitrate, nitrite, nitrate, etc etc) and converting them into less/non toxic chemicals that can be removed by the protein skimmer. And then there's zeovit where the mixture of zeolytes is doing something confusing in the mix too. Zeolytes are mostly carbon based which could possibly explain the efficiency of zeovit's bacteria. Zeolytes are being studied right now along with graphite for carbon-based nano-technology.

The results of bacteria products I think are more interesting to me than natrual nitrification/denitrification because of the results I've seen with my own eyes in tanks running a biological supplementation product. I think the real mystery of these bacterial products is that they're proprietary products that we can't really replicate on our own. These companies have already performed a lot of research and figured things out that work. It makes me wonder if any hobbyists will eventually figure out what's "in" zeovit and reef-fresh and the rest.

StirCrazy
11-24-2007, 05:17 PM
Oh the fun ones I miss when I am gone.

OF course liver rock removed nitrate, well that is if it is in good condition and the right type. it has to have enough porosity and they type of fissures that can create anoxic areas.

I know when I bought my tank I took 240lbs of established liver rock and put it into a cycling tank with 30ppm nitrates. in 24 hours my nitrates were never seen again.

now what makes bad rock or reduces the amount of nitrate reduction. Coraline algae. the more this covers the more it seals. That is why I think people who do racks for there rock to get by with less rock are just asking for trouble down the road. I personally thing you need to have a substantial amount of rock that doesn't get light that way Coraline can't seal it up.

when I had the stuck heater incident, I had a lot of coral dying in my tank in efforts to save them (was a heavily stocked coral tank and everything died overnight) and still not one nitrate measured as I had enough rock to handle the on slot of ammonia, nitrite, nitrate.

Steve