Do deep sand beds really help remove nitrates?

[Ram]

I was reading that sand beds of less than 3 inches lack anaerobic bacteria that turn nitrates into nitrogen gas. Does this mean my 1 inch sand bed will promote nitrate retention? I have also read that the fine particles don't allow waste to accumulate underneath any depth of sand, as crushed coral does, so reduces nitrate accumulation. Which is true?

 

[TriggerThis]

Both.
A deep sand bad uses sugar fine sand and detritus doesn't settle into it, just stays on top,
It also creates a low oxygen environment inside it where the special bacteria likes to grow.

Your 1" sandbed will not promote nitrates but it deff won't make them better.
More neutral
It's just a sandbed at that point.
As long as it's not crushed coral, the crushed coral will contribute to nitrates as large Debris will get trapped all through it

 

[Reefaddict305]

@Ram in order to be successful with a DSB you have to have 4 inch dsb, also with no crush corals cuz if you do you will run into major problems. You can go with sand thats in between 0.1 to .05 in grain size. Also you need to have beneficial animals that will help you clean that dsb.

 

[TriggerThis]

And animals that won't disturb it

 

[Wiz]

The anaerobic part is true. If your sand is less than 3" its probably a good idea tto vacuum regularly. Deeper beds do have that area and are more helpful with the cycle. They also promote microfauna which is al so helpful if you don't have predators of them. Crushed coral has cavities that trap debris and cause more nitrates in the system. I'm not sure about the penetration issue. But if there is less space in the substrate than less debris can become lodged. I have a dsb in my fuge and about 1/2" in my display. Dsb can be great if done properly. If you have not already, read this article. Very helpful:)

http://www.ronshimek.com/deep_sand_beds.html

 

[merlberg]

Both.
A deep sand bad uses sugar fine sand and detritus doesn't settle into it, just stays on top,
It also creates a low oxygen environment inside it where the special bacteria likes to grow.

Your 1" sandbed will not promote nitrates but it deff won't make them better.
More neutral
It's just a sandbed at that point.
As long as it's not crushed coral, the crushed coral will contribute to nitrates as large Debris will get trapped all through it

So are there any cons to having DSB as there are with sandbeds that are less than 3 inches?

 

[TriggerThis]

You can't have fish that burrow under the sand, no animals that sift or eat the critters in the sand either.

No sand sifting stars or gobies, pistol shrimp, eels, no fish that eat pods, like mandarins and some wrasses, no sea cucumbers,

 

[merlberg]

This might be a silly question but does the type if sand bed apply to both reef and fish only

 

[Randy Holmes-Farley]

I was reading that sand beds of less than 3 inches lack anaerobic bacteria that turn nitrates into nitrogen gas. Does this mean my 1 inch sand bed will promote nitrate retention? I have also read that the fine particles don't allow waste to accumulate underneath any depth of sand, as crushed coral does, so reduces nitrate accumulation. Which is true?

A thin sand bed may not reduce nitrate. That doesn't mean it promotes nitrate retention, just not promoting reduction.

Larger sand particle sizes may collect more detritus. If you accumulate detritus that would otherwise be removed, that will result in more nitrate and phosphate released from the detritus as it is degraded. If the detritus would otherwise collect somewhere else (like behind rocks), it may not matter where it accumulates and breaks down. FWIW, I just let mine collect in my refugia and sumps. I just ignore it.

The nitrate reduction capability of rock and sand will be promoted by organic carbon dosing, which spurs those bacteria. :)

 

[merlberg]

You can't have fish that burrow under the sand, no animals that sift or eat the critters in the sand either.

No sand sifting stars or gobies, pistol shrimp, eels, no fish that eat pods, like mandarins and some wrasses, no sea cucumbers,

Oh wow! But that's if you have a DSB right?

 

[Randy Holmes-Farley]

FWIW, I had some deep sand beds in my refugia for several years. 6-8 inches of fine aragonite. At the end of that time, I didn't think it was doing much useful (or detrimental, for that matter), so I got rid of it.

 

[Randy Holmes-Farley]

So are there any cons to having DSB as there are with sandbeds that are less than 3 inches?

I cannot think of a con to a thin sand bed that doesn't also apply to deep sand, but there are not many cons (aside from the possibility of detritus) to a thin one. :)

 

[merlberg]

I cannot think of a con to a thin sand bed that doesn't also apply to deep sand, but there are not many cons (aside from the possibility of detritus) to a thin one. :)

Ok thanks

 

[Ram]

My logic was, well, how can nitrates get deep enough in the sand bed to be effected by anaerobic bacteria if it isn't supposed to be able to penetrate such depths in the first place.

Also, I gather that one can have the same benefit of a dsb by creating a dsb in the sump and a thin bed in the tank.

 

[Wiz]

This is why it's so very important to not have sand sifters in a DSB. The way the water gets to the bottom is through the cavities caused by microfauna. So worms, Non predatory snails, and pods that make their way to the top will create a hole allowing the dirty water to sink into the sand bed. All this is outlined in the article that I posted. And I think that a DSB fuge is definitely the way to go as my system is exactly that. Lol

My logic was, well, how can nitrates get deep enough in the sand bed to be effected by anaerobic bacteria if it isn't supposed to be able to penetrate such depths in the first place.

Also, I gather that one can have the same benefit of a dsb by creating a dsb in the sump and a thin bed in the tank.

 

[Randy Holmes-Farley]

My logic was, well, how can nitrates get deep enough in the sand bed to be effected by anaerobic bacteria if it isn't supposed to be able to penetrate such depths in the first place.

Also, I gather that one can have the same benefit of a dsb by creating a dsb in the sump and a thin bed in the tank.

It is a slow penetration of nitrate and organics (necessary for the process; people sometimes forget about this part of the process) into regions where O2 penetration is also slow.

The reason a thin sand bed doesn't work is because penetration of all of these (but most importantly, O2) is too fast.

 

[chimmike]

Glad I searched on this topic. Considering another DSB on a new tank I'm planning. Maybe I'll have 1/4 of the return flow dump into a DSB chamber with some non-predatory snails. I had a DSB in the past, never had issues with it, but didn't do any nominal amount of monitoring.

Side note: Randy, it's so nice to see you posting here. Years ago I was elsewhere and you were legend but didn't post much.

 

[brandon429]

The ability to attain natural nitrate reduction via degasing (via live rock, dsb) is so inconsistently harnessed, they had to invent biopellets

the dsb/low nitrate approach was ran through 2 mil reefs 1998-curr

then came biopellets to make repeatable good

its not that its unattainable, I believe huge amounts of live rock to very low fish bioloading can pull it off, but so few people set up tanks in that ratio while using a dsb that you can expect any depth to cause nitrates and not lower them. When the results change off 25 yrs documentation, biopellets w go away and berlin systems w be all the rage again



I have a dsb that reduces nitrates btw so don't flame me too bad :) for calling nay on them by and large

a golden ratio: no fish, 5 pounds per gallon porous coralline lr, kept organically unplugged via violent water changes, correct grain size, 6 inches, 9 yrs, and visual gas production w benthic life interspersed

I found in long term studies that even truly reductive dsb's using tiny reef models will become nutrient sinks if you don't blast clean them. critters in the sandbed contribute to waste sinking, not lower it, nothing eats detritus in a sandbed but a monsoon storm w full beach ejection occasionally sure does.

 

[CastAway]

Just a thought, but key to a nitrate reducing DSB is the slow but sure advection of water through it. You need water movement and some corresponding pressure differentials at the surface of the DSB - advection enough to bring nitrate laden water to the anaerobic areas, but not so much as to prevent the anaerobic areas in the first place. Right?

 

[brandon429]

to me that sounds like each tank with a dsb though, they tried for decades to get NNR on any possible consistent basis using *typical tank arrangements, namely just dsb's, and it was such a long shot biopellets came about instead since the other really doesn't work with todays typical reef tanks

plant binding always was consistent but not true in-tank NNR without very special planning, the kind of planning we don't see across forum tanks. Randy keeps a trash can full of lr, that's an unusual and likely functional ratio

there are 5 gallon bucket remote dsbs, reverse dsbs im sure with changing degrees of working

but theres biopellets to amend all the variability~