Are the risks of having a deep sandbed exaggerated?

[CHSUB]

Seems with the current fad of high nitrates, why would the “new kids on the block” want a DSB?

 

[IceNein]

So I am missing something here…. What’s a plenum?

A plenum is a space below the sand bed. The water flows down through the sand bed, and then you have a water permeable barrier at the bottom of the tank that creates a void, and then you have a riser tube where you pump water up out of the plenum.

 

[vlangel]

There is some truth to this. Myself, back when I was a regular on 3Reef, there was a lot of talk about DSB vs. ummm, Not So DSB. Never knew anyone directly who had any issues.....only the stories. But those stories have remained very consistent over the past 17 years. Same stories. Same concerns behind them. So, personally, I think there's something to it. I can't help but think that the odds of a negative outcome are greater, but on the other hand, there are definite benefits as well. Take the good with the bad........

Like you, I have also heard the stories. I was hoping that with so many hobbyists on R2R that I could hear 1st hand accounts, either for the good or for the bad regarding DSBs. So far the only 1st hand accounts that I have heard were success stories of folks who had DSBs. That encourages me that a DSB is maybe not as risky as reef keepers fear which is what I have always believed from my own personal experience.

 

[vlangel]

Seems with the current fad of high nitrates, why would the “new kids on the block” want a DSB?

The reason I like nitrate reduction is because I like to keep a lot of fish and I like to feed them well.

 

[CHSUB]

The reason I like nitrate reduction is because I like to keep a lot of fish and I like to feed them well.

You don’t have to tell me, I keep no3 undetected with hobby testing.

 

[CoastalTownLayabout]

Like you, I have also heard the stories. I was hoping that with so many hobbyists on R2R that I could hear 1st hand accounts, either for the good or for the bad regarding DSBs. So far the only 1st hand accounts that I have heard were success stories of folks who had DSBs. That encourages me that a DSB is maybe not as risky as reef keepers fear which is what I have always believed from my own personal experience.

The stories always seemed to be cautionary, in fact from memory I recall the RC thread being titled something along the lines of DSBs are a Ticking Time Bomb.

I remember a small number of DSB systems that had issues because of powerheads falling from mounts and excavating the bed. Otherwise, it was usually cyano being the most reported nuisance.

Of course some of those who removed their DSBs out of fear reported foul smelling lower beds but that doesn’t really count as a problem.

 

[IceNein]

Like you, I have also heard the stories. I was hoping that with so many hobbyists on R2R that I could hear 1st hand accounts, either for the good or for the bad regarding DSBs. So far the only 1st hand accounts that I have heard were success stories of folks who had DSBs. That encourages me that a DSB is maybe not as risky as reef keepers fear which is what I have always believed from my own personal experience.

I think that the flaw in your logic is survivorship bias. If someone has a DSB and for what ever reason, in what ever way it crashes their tank, then often they do not stick around the hobby. So of all DSB users, you are more likely to hear from someone who has not had a tank crash because of them.

Maybe they're great. I really don't know. I would absolutely love to see some long term tests. Personally I love the idea of more life, more biodiversity.

Again this goes to the biggest problem in the hobby is that 90% of everything is anecdotal.

 

[Randy Holmes-Farley Verified Community Expert]

So far the only 1st hand accounts that I have heard were success stories of folks who had DSBs. That encourages me that a DSB is maybe not as risky as reef keepers fear which is what I have always believed from my own personal experience.

I posted a first hand account to this thread that wasn’t a success. I didn’t think it did anything.

I’ll also note that it’s not clear to me whether at least some of the successes in this thread would have been any less successful without it. One person, for example, compared dsb plus macroalgae to water changes and skimming only. Is that a dsb success or a macroalgae success?

They may well be useful, but I am not convinced it’s a great way to go.

 

[sgdnycct]

A plenum is a space below the sand bed. The water flows down through the sand bed, and then you have a water permeable barrier at the bottom of the tank that creates a void, and then you have a riser tube where you pump water up out of the plenum.

Clarifying a point about my version of a plenum: I have a 2 inch layer on the bottom with a mesh plastic covering it. I then have the rest of the sand on top of this. I don’t have a hollow area or exhaust piping. I do this to keep anything from disturbing the deepest layer of the sand bed.

 

[areefer01]

Like you, I have also heard the stories. I was hoping that with so many hobbyists on R2R that I could hear 1st hand accounts, either for the good or for the bad regarding DSBs. So far the only 1st hand accounts that I have heard were success stories of folks who had DSBs. That encourages me that a DSB is maybe not as risky as reef keepers fear which is what I have always believed from my own personal experience.

Sometimes when something is repeated long enough it becomes truth. I am not saying that is the case here but it is something to consider.

 

[VintageReefer]

I’m from the RC forum back in the day. Maybe 2010ish? and I ran a a 6-7”
DSB on a system for about 6 years. The system never had any nitrate or phosphate issues for 5.5 years. I was younger and less experienced and felt the DSB was a key part of my systems stability and numbers. And it could have been. In the final 6 months the system started to crash, fast. Nutrient spikes, algae issues, then chain reactions of losses. To this day, I am not quite sure what happened but it sounds like old tank syndrome and I feel the DSB was a factor. I was always thinking not to disturb it, for fear of toxins coming out from the bottom layers. But maybe I should have stirred or cleaned it periodically.

I switched to running “medium sand bed” that are approx 3-4” and have had no issues over the last decade

 

[maroun.c]

Memories memories :)
We used to use twi sand thicknesses fine for the deeper portion and a bit thicker for the top one to be able have a good flow without sand shifting ...
A very heavy microfauna we don't see anymore not sure ifnit was due to live rock or if it's because our tanks are too clean to sustain and that would constantly move the sand for water tonmove through very closely or that's what we believed .
One difference we see now that can make DSBs work is the lighter rockscape VS 25 years ago where we had tanks filled with rock, so the more water sand contact we have now and better flow all over might make it better for DSBs
Yet loosing 4-6 inches of space in now shallower tanks is not really an option.
One trend that appeared late in the DSB era was RDSB or remote DSB in the sump or in a bucket with good flow above it which could be reset. Bucket was a good option as we could have strong flow above the sand and total darkness with closed lid which encouraged microfauna to grow faster. Then afraid you reached old tank syndrome start a new bucket then toss the old one few months later.
Why is it difficult to experiment , is because tanks struggled more with lack of nutrients so there was no need for nutrient reduction methods lately, also experimenting means a 10-15 years time and many tanks crash from other reasons or are shut down way before that.

 

[56longroof]

There is some truth to this. Myself, back when I was a regular on 3Reef, there was a lot of talk about DSB vs. ummm, Not So DSB. Never knew anyone directly who had any issues.....only the stories. But those stories have remained very consistent over the past 17 years. Same stories. Same concerns behind them. So, personally, I think there's something to it. I can't help but think that the odds of a negative outcome are greater, but on the other hand, there are definite benefits as well. Take the good with the bad........

Myths are present in all hobbies. Some are loosely based on facts and some are complete BS. I believe the bad rap DSB have gotten was from the lazy or uneducated. It's easy to pass blame on to something else instead of admitting the real problem.

 

[PharmrJohn]

Myths are present in all hobbies. Some are loosely based on facts and some are complete BS. I believe the bad rap DSB have gotten was from the lazy or uneducated. It's easy to pass blame on to something else instead of admitting the real problem.

Thats a good point. But I can see the theory behind the claims. But in the end, it could be just that. But, on the other side, there are generally some truths behind myths. However misplaced.

 

[vlangel]

The stories always seemed to be cautionary, in fact from memory I recall the RC thread being titled something along the lines of DSBs are a Ticking Time Bomb.

I remember a small number of DSB systems that had issues because of powerheads falling from mounts and excavating the bed. Otherwise, it was usually cyano being the most reported nuisance.

Of course some of those who removed their DSBs out of fear reported foul smelling lower beds but that doesn’t really count as a problem.

That is the same thread I read on RC and I remember reading at least one account of a powerhead falling and trenching the sandbed. That is something that can definitely happen and so it is a valid risk to be assessed.

I have had cyano on my DSBs but then I also have had cyano on the SSB I had in my seahorse tank so I don't know what that says except cyano happens. LOL

 

[Randy Holmes-Farley Verified Community Expert]

Another thing to think about here, is that the O2 is diffusing, it is just getting used up as it diffuses into the top layer.

It really depends on the top layer fauna to overturn the sand and creating their own organics. I do not a believe a DSB with little overturn works as well as one with lots of overturn.

I’m not sure how all that math works out. How is the O2 getting used up that does not itself produce nitrate? The organics that you propose are driven into the sand by fauna themselves contain N. Where is that N going?

I contend the theory is flawed. Doesn’t mean sand beds don’t lower nitrate, but I don’t see how they can do it for the reasons folks suggest.

 

[vlangel]

I think that the flaw in your logic is survivorship bias. If someone has a DSB and for what ever reason, in what ever way it crashes their tank, then often they do not stick around the hobby. So of all DSB users, you are more likely to hear from someone who has not had a tank crash because of them.

Maybe they're great. I really don't know. I would absolutely love to see some long term tests. Personally I love the idea of more life, more biodiversity.

Again this goes to the biggest problem in the hobby is that 90% of everything is anecdotal.

You are correct in this thread is NOT a conclusive proof whether DSBs are safe or not. The parameters of each person's tanks have too many variables to compare apples with apples. This thread is more about generalities. I have just read so many posts about the dangers of DSBs and lately almost never see anything positive about them. I was curious if there were still folks out there like me who used them and was their tank flourishing.

 

[World Citizen]

My experience could indeed be something else and not the RDSB. I didn't have the DSB in the tank, I had it in a part of the sump.

I did it without the plenum (learned a new word today, thanks) because my emotional logic thinks it just needs to be a thick fairly stable layer of sand.

I am telling myself things happen in these layers and it helps to have a small spot of this RDSB. I wouldn't stop using other filter methods. It would be a additional filter option in the tank. A new area for "life" to live.

If I would be forced to answer I think about 1/6th to 1/10th of the footprint of your display tank.

 

[vlangel]

I posted a first hand account to this thread that wasn’t a success. I didn’t think it did anything.

I’ll also note that it’s not clear to me whether at least some of the successes in this thread would have been any less successful without it. One person, for example, compared dsb plus macroalgae to water changes and skimming only. Is that a dsb success or a macroalgae success?

They may well be useful, but I am not convinced it’s a great way to go.

Ha ha, yes I was thinking either they are a disaster or a success and that's not true as you astutely pointed out. In fact, even though my present tank is flourishing, that may not be a result of the DSB. I have also kept successful SSB tank and BB tank. I will say that for me the DSB is less maintenance than the other two which is another reason that I like them.

 

[vlangel]

I’m from the RC forum back in the day. Maybe 2010ish? and I ran a a 6-7”
DSB on a system for about 6 years. The system never had any nitrate or phosphate issues for 5.5 years. I was younger and less experienced and felt the DSB was a key part of my systems stability and numbers. And it could have been. In the final 6 months the system started to crash, fast. Nutrient spikes, algae issues, then chain reactions of losses. To this day, I am not quite sure what happened but it sounds like old tank syndrome and I feel the DSB was a factor. I was always thinking not to disturb it, for fear of toxins coming out from the bottom layers. But maybe I should have stirred or cleaned it periodically.

I switched to running “medium sand bed” that are approx 3-4” and have had no issues over the last decade

Thank you Vintage Reefer. I appreciate hearing your experience with a DSB. I would certainly categorize your experience as negative and that adds validity to the risks of having a DSB.