The problem with DSBs

[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

__________________

 

[Killerdrgn]

But wouldn't the amount of the ammonia created from the anoxic zone have to pass back through the aerobic zone to actually get into the water? and then wouldn't that have another shot at going though the anerobic zone to become nitrogen gas?
Also wouldn't dense LR also have the same effects?

 

[Killerdrgn]

Also wouldn't this also apply to coil denitrators? As they work on the same principle.

 

[Paul B]

But wouldn't the amount of the ammonia created from the anoxic zone have to pass back through the aerobic zone to actually get into the water? and then wouldn't that have another shot at going though the anerobic zone to become nitrogen gas?
Also wouldn't dense LR also have the same effects?

I would imagine it would but now we have three different forms of bacteria acting on the wastes. One of them converts ammonia to nitrate, one of them converts it back to "ammonium" and a third converts the ammonium back to nitrate. I am sure not all of the converted nitrates get turned back to ammonium but it still short circuits the theory that all of the nitrates in the lower portions of a DSB is not eliminated as nitrogen gas. The deeper, less oxygenated layers are still converting that nitrogen which would have been eliminated, back to a harmful substance.
Don't forget, I did not invent this, I am just reading it.
The article also mentions that too much rock will have the same problem.
It would make sense because there is a lot of water changing going on in this hobby.
If a DSB is so good at controlling nitraters, then why do so many people have high nitrates even after they change the water.
My nitrates are very low and I have a slow RUGF in an overstocked very old tank and I change very little water. There are no anerobic areas in my tank.

 

[House of Laughter]

Paul, then how do you (not you per say) explain the ocean and it's deepest sand bed?

House

 

[Paul B]

Paul, then how do you (not you per say) explain the ocean and it's deepest sand bed?

I don't know, but then how do you explain my low nitrates without a DSB and very little water changes?

This is the letter Bob Goemans just wrote back to me

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 – 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

 

[BZOFIQ]

I don't know, but then how do you explain my low nitrates without a DSB and very little water changes?

This is the letter Bob Goemans just wrote back to me

You are not overfeeding!

 

[Paul B]

You are not overfeeding!

I have over 25 fish, maybe 30 in a 100 gallon tank with no sump. Many of them are spawning so I feed them at least twice a day along with feeding live baby brine shrimp twice a day in addition to live worms. I add bacteria and mud from the sea.
There is no denitrator coil and I removed two five gallon buckets of rock last year and another two buckets the year before. My substrate is over 40 years old.
The tank is in total equilibrium, Why?

 

[House of Laughter]

Must be the bottle

all kidding aside - when you put the ocean into a box, contain it and mess with proportions, things change in reference to NSW - my opinion.

I think you have good rock, good flow proper balance in your substrate (and efficient fish

House

 

[Paul B]

I think you were correct with the bottle theory

 

[MikeyZO]

The tank is in total equilibrium, Why?

Was it always from day one? Or as you carted off rock and substrate, did it eventually come to an equilibrium? How many years was it running before this happened? The theory I am getting at is that most have tanks running for a few years with these high nitrate results, yours has been up for almost 40 years if I remember correctly. The Ocean has been running for millions of years. Maybe it just takes a long time for the system to actually "stabilize" itself... your 40 years in that size tank could be the equivalent of hundres or thousands in ocean time.

Ok maybe a bit of an exaggeration there but you get the idea. Eventually the three bacterial zones youre speaking of just come to their own equilibrium, which most of our tanks have yet to reach.

 

[Paul B]

Mikey, could be, my tank has a few more years to get to the age of the oceans and I really don't remember how long my tank has been in equilibrium but I think I removed the bioballs maybe 15 years ago and since then my nitrates measured zero on aquarium test kits but they are really five when I had it professionally tested.
The nitrates ran in the 20s before that.
I have always felt the technology in DSBs was flawed. In a system like that which is supposed to remove nitrate why is so much water being changed.
I only change water because I feel the animals need a replacement of trace elements but I never changed water due to nitrate levels.

 

[Davidl919]

I recently ran about a 2in sb and I am considering going with a 6 in. With this new development in research was there a minimal number or was it just anything considered dsb.
I, like you, Paul, never really trusted the concept of dsb, understood it but always doubted it, without some type of recirculation by means of nassirus, sand sifter stars, etc. I hope more research is done on the matter and more results are posted..... Thanks For the post. Paul.

 

[Mreefer]

is this just a theory or a fact? has anyone actually isolated bacterial strains in sand beds that perform each of these biochemical functions (nitrification, denitrification, ammonification) in lab settings? has anyone measured the O2 content of a successful dsb and shown that well defined 3 zones do exist? seems like an interesting read. how do you know it's not just the same bacteria that does all these biochemical reactions. the bacteria deep in the sandbed may not be obligate anaerobes but facultative anaerobes that can make energy using both fermentation and respiration and may inhabit all layers of the sandbed.

for the dsbs that fail, what grain sizes of sand were they using and how deep. the smaller the grain sizes, the more bacterial substrate and more bacteria to convert nitrates to nitrogen gas.

an interesting experiment is to take 5 gallon tanks and fill them with dead aragonite of 0.1mm to 1mm grain sizes at 1,2,3,4 and 6 inches, an hob filter and starter live sand from an established tank and ammonia source. if this theory is correct, then we would see high nitrates (1-2 inches dsb, not enough substrate to make an effective denitrator) lowering to midpoint (around 3-4 inches dsb, balance of all 3 bacterial species according to theory) and back to high nitrates as you get deeper dsb (6 inches because there are more bacteria converting nitrogen gas back to nitrates, according to the theory).

 

[Paul B]

Mreefer, no it is fact accumulated from research. I can type all the scientific papers where this research came from but it would take too long so I will post a few.
(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

 

[fernandokng]

Yet another interesting theory on DSBs. With this "new" information, So, how do we exploit DSBs for our needs?

1. What is the "now" recommended depth? Used to be 6+ inches before...
2. How do we "maximize" that zone that allows denitrification? Is it even possible?
3. Can we conclude that efficiency can be given by surface area rather than depth of the sand bed?

 

[Paul B]

Fernandokng, from speaking to Bob and seeing my own tank, I think a DSB that uses too fine a sand or is deeper than a couple of inches will have nitrate problems.
He and me have always recommended a shallower bed or a gravel bed. The problem with a gravel bed is that it needs to be cleaned. I do that a few times a year by putting a restriction on my diatom filter and powerwashing the gravel. The beneficial bacteria will again start functuning very shortly and the substrait will be invigorated like new and will run to it's capacity. I use a RUGF but it is essentially a gravel substrate with a plenum. I just happen to run a little water under the plenum.
But, being my tank has been running so long with low nitrates makes me assume that my substrate is controlling the nitrates, all the nitrates. I never needed a refugium or denitrifier. Read on here how many tanks with deep DSBs have to change water every week or so to control nitrates. Why would you do that if a DSB is the holy grail of nitrate removal.
They work, but they have a few issues that may be able to be corrected by removing some sand and making them one and a half inches instead of 6"
UG filters also don't work but if you tweek it the proper way, they also 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.

(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

 

[KathyC]

Paul..interesting discussion!
I don't think there are many here that are running DSB's of 6+ inches. The majority of the folks dealing with high nitrates are running SB's in the 1-3 inch depth (judging from the pics in peoples tank threads).

So why aren't their SB's doing the job properly, is it due to them having critters that stir the sand and therefore cause the SB not to do its job by constantly aerating it and disrupting the layers of bacteria that are necessary?

While you are running a RUGF with water circulating to it, that is wonderful for your tank since it keeps your nitrates nice and low, but it is not likely that the folks here will be taking their tanks apart to do the same, so what is the solution for them?

Are you stilling running the algae scrubber on your tank? Is that also helping your tank in some way?

I'm curious about this answer (in part) from Bob:

Water changes are ?not? the proper way to reduce nitrate ? 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

and this from the article you quoted:

The article also mentions that too much rock will have the same problem.

More about the 'root cause' would be appreciated, and how much rock is too much?
Also curious why the coil denitrators work.

Is it possible to ask Mr. Goemans if he could drop by here and answer some of these questions directly?

 

[Paul B]

Kathy Bob lives in Utah, I will ask him if he would post here. I don't know if he will.
He was at my house in the early ninetees (I think) and he was in his fiftees then.
According to him, any DSB with fine sand is going to contribute to nitrates.
Don't forget Kathy, I did not write this, I am only posting what the research reads.
I also don't feel "critters" actualy burrow much in a DSB. They can not go where there is no oxygen. The research states that any area that is totally devoid of oxygen or almost so, harbors these bacteria that convert nitrogen gas back into ammonium which may become converted back to nitrates but the bacteria living in areas with low, but not "no" oxygen. He states that a gravel bed or a corser sand bed would be better.
My algae trough has not had any algae in it in over a year and there is very little algae in my tank except for a very short red algae that I think is from the Sound where some of my water comes from.
That trough is more to eliminate the ozone from my skimmer and to oxygenate the water. It was an experiment and it may do nothing.
Bob's answer about changing water to reduce nitrates is the same thing I have been saying for years. A tank should be in equilibrium and water should not have to be changed to control nitrates. They should be taken care of entirely by the bacteria in your tank. Why even have a DSB if your nitrates are constantly climbing? The sole purpose of this type of system is to control nitrates. If that is not the case, the thing is not working.
I am not asking people on here to change to anything. I am happy with my tank which is in equilibrium and I only change water to add trace elements never to lower nitrates.
Kathy, as you know my tank is almost 40 years old. My nitrates read 5 after being professionally tested a few weeks ago. My fish are breeding so I overfeed. I also add live baby brine shrimp twice a day. I change 20% of the water four or five times a year. There are about 25 or 30 fish in my 100 gallon tank. I am sure there is gunk in there from many years ago.
This past year I removed almost 4 five gallon buckets of rock to make the tank more open.
My nitrates must be taken care of someplace.
As for denitrification coils, I would imagine that if the coil is too long that would have the same bacteria problems but I never built one to test because I never needed to so I can't answer it.
Like I say, I am only posting an article. Think of it as you would anything you read in this hobby. You can disreguard it or read into it.
I would think that if I have nitrates in my tank, I want to know why.
Maybe this research is nonsense, a lot of stuff we read is. But ask how many people on here have to change water every week to control nitrates.

 

[KathyC]

Do you have the link to the article you addressed in your first post on this thread? Thanks