Latest theories on NNR?

[vikubz]

I have been searching for a thread from a few months ago about some new ideas as to NNR and how it is achieved in reef tanks. If I remember correctly it was proposed that the anaerobic bacteria inhabit a relatively narrow zone beneath the aerobic bacteria and not the entire depth of the sand bed. Does anyone recall the thread and are there any new developments in this area?

Thanks!

 

[Gravesj1s]

-Vikubz,Hi.

I think the thread your refering to was entitled New Nitrate Theory.

In short there isn't anything new about the theory proposed by Bob Goemans.There is mention of advective flow in the thread whitch is a new idea to me.But I still have trouble with the whole deep sand bed "theory".Little if any evidence exists it ever worked as aquarium literature made it out to.
The advective flow is ,in theory anyway,proposed to counter carbon limiting much deeper into the substrate as well as no3 and po4.I cant help think the substrate would act as a mecanical filter and eventualy clog.From what little I got of someone to respond is you would still be relying on some worms to stir the substrate.This makes little sense to me ,why would a worm that needs oxygen go deep into a substrate when it could get at food in the shallower regions.I dont know,I dont get it.

 

[vikubz]

I found an article by Goemans which goes over this info. Google "Sandbeds-Part I" and Part II. If I understand correctly, he states that in our home aquariums, the DSB does not develop an anoxic zone but rather a large anaerobic zone, which converts nitrate to ammonium, which we all know is a compound we are trying to avoid. So by attempting to create an anoxic zone, we are putting more ammonia back into the water column?

At any rate, he mentions that in DSBs the anoxic zone has been shown to be very limited.

What I am looking at is the effectiveness of the "DSB in a Bucket" idea. Based on Goemans' article, the actual anoxic area in a 5 gallon bucket would be so small that I don't see how it could manage any meaningful NNR in the typical system we see in the hobby. I think people's success at nitrate control has more to do with other factors in their system, such as macroalgaes, heavy skimming and regular water changes than it does with DSBs.

 

[Gravesj1s]

I haven't read the artice yet but theres a short coming in Goemans theory.No known bacteria that consumes Nitrate and leaves ammonia/ammonium as a byproduct that isn't photosynthetic.Cyanobacterium is the only type I know of that is.I read the thread (new nitrate theory)and that seems to be the opinion of the majority.

 

[Gravesj1s]

I haven't read the artice yet but theres a short coming in Goemans theory.No known bacteria that consumes Nitrate and leaves ammonia/ammonium as a byproduct that isn't photosynthetic.Cyanobacterium is the only type I know of that is.I read the thread (new nitrate theory)and that seems to be the opinion of the majority.

Typo above should of read:

Cyanobacterium is photosynthetic,so I dont know how it would be fixiating nitrogen without light.

 

[ctenophors rule]

Another thing i would like to point out. I have been having this debate with another reefer for sometime, and finaly i decided to experiment. I made a 5 inch deep sand bed in one of my ten gallon tanks that are plumbed into my seahorses breeding facility. the sand produced a dark black spot near the bottom. this he explained to me was 'highly beneficial anaeroic bacteria' within three weeks it is now within a 1-2 inch range from the top of the sand bed. more over it actively fluctuates. it experieces die offs, and then re grows.

now, from what i have read, bacteria is most efficient when it is young (somewhere near 75% more). so realy, if the anaerobic bacteria in the top 2 inches of the sand bed is always fluctuating from living and nonliving, isn't that the only bacteria you realy need? i mean that 25% is also taking a lot of water space that could be used for nutrient dissolution. and the money spent on all that extra, basicaly useless sand could have been used to get a better protien skimmer, etc.

 

[vikubz]

What I took away from Goeman's article is that the extra sand is actually generating NH4, so it would not only be extraneous, but possibly have a negative effect. The denitrifying zone is a narrow band just below the aerobic area. Perhaps this is why some have reported a positive effect from only a couple inches of substrate.

I am curious to know exactly how the NO3 to NH4 process occurs as well. At any rate, it sounds as if no matter how deep your dsb is, the actual denitrifying zone would be very narrow.

 

[GOLFREEFER]

The only reason I see to having a deep sand bed of more than a few inches is so incase it gets disturbed there is always a oxygen free area to take its place.

Example- If you have a fish or powehead, etc blow away the top 2 inches of a 3 inch sandbed then you no longer have anaerobic area but if it is deeper you will always have that oxygen free area.

With all that being said, I personally will never advocate the use of DSB for denitrification, I believe they are nutrient sinks that are more trouble than their worth. I know people can and do have success but it takes just the right amount of sand manipulation to keep them functioning and healthy. I prefer easier to control methods of Denitrification.

 

[elegance coral]

If ammonia is produced from nitrate in the anaerobic environment of a DSB, how will the ammonia make it through the aerobic bacteria on top of the sand to effect the critters of the tank?

 

[BadSquishy]

I'm not sure how much I understand - I think we assume "one" NNR pathway, but there are probably many...with many participants.

I don't run a DSB - I run A Reverse Flow Under Gravel with a plenum, have no sump or refugium - have a high bio-load and no nitrates - I don't quite know how its working. I've been trying to understand it. Some articles (maybe old news).

Marine Crenarchaeota
http://www.pnas.org/content/103/33/12317.full

and

Coral-associated ammonium oxidizing Crenarchaeota and
their role in the coral holobiont nitrogen cycle
*
N. Siboni1, E. Ben-Dov1,2, A. Sivan1, A. Kushmaro1,3

 

[GOLFREEFER]

If ammonia is produced from nitrate in the anaerobic environment of a DSB, how will the ammonia make it through the aerobic bacteria on top of the sand to effect the critters of the tank?

Good observation, but maybe the amount of amonia may well overwhelm the processing capabilities of the DSB.

 

[vikubz]

The ammonia probably would not make it past the aerobic bacteria, but as we know, the ammonia would be converted to nitrates, so it seems that you would never get ahead.