New Nitrate theory

[Paul B]

I have been wondering for years why so many people have high nitrate forcing them to change large volumes of water when they have DSBs which are supposed to eliminate nitrates through anerobic bacteria.

Some people have even resorted to adding remote DSBs or constructing them very deep.
This does not help and new research explains why.
I recently read a "Sea Scope" publication written by Bob Goemans and it confirms what I have been saying for years.
DSB technology is flawed, but we never knew exactly why.
Yesterday I called Bob at his home to discuss the article.
We think of two different types of bacteria that inhabit the two zones in an aquarium. One is aerobic heterotrophs which live in the upper layer of a DSB and every other oxygenated surface in a tank. The other is Anerobic bacteria that inhabit anerobic or very low oxygen areas.
These anerobic bacteria (we thought) are the ones that convert nitrate to harmless nitrogen gas which harmlessly bubbles out of the water.
Now we find that there is another form of bacteria that lives in close association with the nitrate reducing bacteria in deeper, less oxygenated layers. These other bacteria are also anerobic but they convert nitrogen back to ammonium. As the ammonium rises from the deeper layers it is again converted back to nitrate and diffuses into the water column.

There are not just two zones in an aquarium but three. There is aerobic or oxygen rich areas, anerobic areas which have very little to no oxygen and anoxic zones which are in between and have a small amount of oxygen. Such an area would be just under the surface of the sand or gravel (or in a slow running RUGF)
The anoxic layer with a small amount of oxygen is where the beneficial bacteria florish which convert nitrate to harmless gas.
If a tank has a large anerobic (no oxygen) area such as a DSB and a small anoxic ( or low oxygen) area, nitrate and nitrite could be converted back to ammonium, then back again to nitrate.

A quote from Bobs article
"This is referred to as the ammonification process. The continueing re processing of this ammonium produced in the lower anerobic level of the substrate, back into nitrite and nitrate in the upper reaches of the substrate, is quite feasable. With any of them-ammonium, nitrite, nitrate-leaching back into the bulk water is quite possable"

So it seems that if we want to reduce nitrate we need to have more anoxic or "low" not "no" oxygen areas. DSBs that are not very deep or gravel beds would accomplish this

 

[spsfreak]

Great to hear of this news\theory Paul. I too have always thought the DSB's were a source of problems from past exp. That is why I have kept BB or very SSB's in my last few tanks.

 

[onetrickpony]

do you think the ammonification process would apply to some of the more dense rock some use

 

[onetrickpony]

 

[PatrickJ]

I've had similar thoughts, if not identical. I think DSB can be still useful, but remote setups are ideal but not practicle in my home.

I am planning to go BB next time around with maybe some sort of carbon source denitrator in place of a DSB.

Denitrators are far more efficent than DSB and take up less space.

 

[Paul B]

do you think the ammonification process would apply to some of the more dense rock some use

Yes, that was also part of the article.
DSBs are OK but deeper is not better. If you can pick up a copy of Sea Scope Volume 23 which is a free pamphlet put put out by Instant Ocean you can read the entire article.

 

[Paul B]

This is the letter Bob just wrote back to me

Quote
"Hi Paul.
Could be those people that keep changing water to reduce nitrate don’t realize that within one to two days after a change the nitrate level returns to the almost the exact level it was before the change. The reason for that is nitrate is flowing back into the bulk water from their sandbed and live rock! Water changes are ‘not’ the proper way to reduce nitrate â€"œ getting to the root cause is the way to go and also that of understanding how those bacterium work in substrates of various kinds, depths, and porosity.
Bob"

 

[gwenvet]

So what's his determination of how deep is too deep? And is it dependent on how large the sand bed's particulate size is? I would imagine that you could get away with a deeper sand bed composed of larger particle size than you could with a very fine sand that would create an anoxic zone at less depth.

 

[IslandCrow]

That's interesting Paul. I always understood that you didn't want to go too deep in your sandbed specifically because you didn't want an anaerobic area to develop. It seems that the suggested DSB depth of 4-6" for sugar-sized sand should still hold valid, though. Although I always thought the main issue was the possibility of hydrogen sulfide being produced, it sounds like if you're indeed avoiding that anaerobic region, you're avoiding this third type of bacteria as well.

So, is this really a flaw in the DSB theory, or is it just that people are misapplying the concept?

 

[Paul B]

So what's his determination of how deep is too deep? And is it dependent on how large the sand bed's particulate size is? I would imagine that you could get away with a deeper sand bed composed of larger particle size than you could with a very fine sand that would create an anoxic zone at less depth.

gwenvet, he just states that we should be limiting the depth of the bed and use coarser materials, also limit live rock.

I would disagree with him about the rock but I have always said sand in a DSB is too fine, not allowing any oxygen to circulate.
I diden't know about these other bacteria that converted the nitrogen gas back to ammonium in a complete state of lack of oxygen.
The article states that we should try to get more anoxic or low oxygen areas and less anerobic or no oxygen areas.

 

[HumanIMDB]

Hrm...having just (last year) setup our AGA92 with 4"-5" of sugar sand in the Display and 8" in the refugium, I am going to ignore this thread until we start having problems.

Paul, any suggestions on how to mitigate this issue if one already has a DSB and doesn't want to go through the hassles of removing it?

 

[Paul B]

Chris, according to this research, DSBs are too deep, allowing those nitrate converters to florish. I would think reducing the substrate to about an inch and a half would do it.

UG filters also don't work but if you tweek it the proper way, they work as my tank proves.
I never believed the concept that "critters" in a DSB burrow under the sand to let in water to be treated. All "critters" need oxygen to live and none of them are going to burrow into a bed with no oxygen, it just aint going to happen. It would be like me crawling into a burning building for no purpose when I can stay up here where I can breathe.
It seems that reducing oxygen, not entirely eliminating it, allows these beneficial bacteria to florish while not allowing the bacteria that re convert nitrate to ammonium to be converted back to nitrates to live.
I am not a chemist or researcher, I am a hobbiest like the rest of you. But I do have an old tank with no DSB with almost no nitrates where I hardly ever have to change water and I never change it because of nitrates.
Don't change anything because of this research, come to your own conclusions. Find people with deep DSBs and see if they read nitrates.


(1) Jaubert 1989, An integrated nitrifying denitrifying biological system capable of purifying seawater in a closed circuit aquarium Bull. Inst.Oceanogr. Monaco. 5:101-106

(2) Gamble. S Goemans, B 2001, The new Wave, Aquarium Husbandry, A More Natural Approach. Weiss Organics, Ft, Lauderdale. FL

(3) www.icsu-scope.org/downloadpubs/scope21/chapter18html

(4) Boudreau B.P. Jorgensen, BB 2002 The Benthic Boundary Layer: transport process and biochemistry, Oxford University Press 2002

There are many more references but I don't want to type them all unless you really need them

 

[HumanIMDB]

We went with a deeper sandbed in the DT to allow for burrowing by a goby/shrimp pair and/or jawfish, otherwise we would have gone with a 1" to 1 1/2" sandbed in the DT. However, having read up on things before setting it up, we saw the "advantages" of having a DSB in the refugium. I guess we will have to see how things pan out and live with the choices we made in the beginning or remove the problem when it occurs.

That said, we'll likely move before this becomes an issue so if further research shows that the DSBs do more harm than good, that will be the time when we'll revamp our setup.

 

[MileHighFish]

This is interesting news, my 1st set up had a 6" DSB in a 60 gal tank, I had a heavy fish load for that size tank and I always dealt with nitrates WC never seamed to be an effective method to elevate the issue. I upgraded to a 100 gal, I never increased the amount of LR used, same fish etc 6'' bed and same nitrate issue that tank was up 5 years and always had 20ppm nitrate. I moved and only took a small amount of sand with me, maybe 1/2" - 1 1/2" in parts, again the same rock etc.. Within a month the tank zeroed out, at the point I started to look at friends that had nitrate issues and all ran DSB. I just moved 900 miles and still running the SSB and no nitrate issue. Since setting the 1st tank up with the SSB I hardly do WC's and the nitrates dont build up.. I went 7 months without a WC about a year ago and with a Pin Point nitrate meter I was testing at 2ppm. So I do think there is something to this new finding..

 

[Paul B]

Milehighfish, It would seem the new studies have some validity.
Anyone else have high nitrates with a DSB?

 

[davewbush]

I've been running DSB between 6 and 7 inches and my nitrates are at 0 and have been there for over a year. I did move the tank in January and the nitrates went up to 10ppm but fell back down to 0 after the first month.

Back in October, November, and the begening of December I got lazy but the nitrates didn't go up. I did how ever have a problem with phos levels at this time.

I test my water today and nitrates, ammonia, and phos were at 0.

 

[Konadog]

Interesting article Paul. This may also explain some of the "old sand bed crashes" that people talk about.

 

[Philwd]

<a href=showthread.php?s=&postid=14574735#post14574735 target=_blank>Originally posted</a> by Konadog
Interesting article Paul. This may also explain some of the "old sand bed crashes" that people talk about.

Can you elaborate further on your thoughts here? I run a black sand bed 4-5" but the grains are larger than a typical DSB. I also run a fuge. Never really had nitrates until ran into a bad stretch at work and let detritus build up in the sump.

 

[MileHighFish]

I think thats what he is saying over time and with out proper or constant attention you might have issues.

 

[Paul B]

Dave, I guess the theory doesen't work on every tank, what can I say? Also your DSB is very young.

Ken I feel all DSBs will crash in a number of years. Eventually the small spaces between the sand have to become completely clogged and being you can't maintain them I do not see any other result. I think ten years (which is just a guess) should do it.
(of course I could be wrong, me not being the God of DSBs)
I do not think any critters will burrow into a non oxygenated area that most likely has hydrogen sulfide.

Phil, according to the research as long as the grains are larger and some oxygen gets through you will have more anoxic zones than anerobic zones and it should be fine.

I am curious, how many people here have a DSB for five or ten years or longer? We will never know the answers to these questions unless we have an accurate count. And out of those beds, how many (if any) read anynitrates?