Pros vs Cons: Deep Sand Bed vs Shallow Sand Bed

[Mike J.]

I think you've been given bad information. Of course, the bacteria will repopulate. Don't fix something that's not broke.

Do you have lots of algae growth on your sand bed? No? Then it is working to reduce nitrates.

 

[The Flying Turkey]

I am currently starting up a 50 gallon rimless cube with a 20 gallon sump and I am still going back and forth trying to decide on a SSB or DSB. After reading through this thread I am leaning towards a DSB, but I have a couple of questions.

My display tank is a 24"x24"x20" cube, would 4" of sand look odd? (I guess that's personal preference, just wondering how deep a tank those of you with DSB's have?)

Another question is about clean up crews. As TriggerThis stated above:

Also note to people wanting a DSB, you can't have sand sifting anything in the tank. They will eat all the benefits of the sand bed. No Gobys, most star fish, urchins, not even some wrasses that will eat the sand critters.

Is there anything I should avoid in a clean up crew? Snails/hermits? What about mini stars and clams? Are there any DSB safe starfish?

I guess are there sand grazers that are DSB safe? Or maybe the list of DSB safe life is a short list?

Thanks for the help!

 

[Eienna]

Hi folks, I have a DSB and I did the unthinkable in ignorance. Last year when I downsized from my 90g I kept about 4" of my sandbed and just added another half inch on top. I was thinking if the majority of anaerobic bacteria died that maybe some would survive and slowly repopulate. I recently was told that was absolutely wrong! Now my tank has been up over a year and seems to be running well and stable. The sand looks healthy with creature tunnels, and not black or oozy looking where I can see. The scape is really nice, so I hate to tear it down if its not dangerous. I'm ok if it not functioning in nitrate reduction since nitrates are not a problem for me, and its only a home for worms and pods. Am I flirting with disaster?

Nah, you were given bad info. Your bacteria is okay. You can ruin it by adding too much sand at once, but 1/4" to 1/2" should be fine. The thing is to avoid smothering the infauna that makes the sandbed work, but it doesn't sound like you did that.

 

[Eienna]

I am currently starting up a 50 gallon rimless cube with a 20 gallon sump and I am still going back and forth trying to decide on a SSB or DSB. After reading through this thread I am leaning towards a DSB, but I have a couple of questions.

My display tank is a 24"x24"x20" cube, would 4" of sand look odd? (I guess that's personal preference, just wondering how deep a tank those of you with DSB's have?)

Another question is about clean up crews. As TriggerThis stated above:


Is there anything I should avoid in a clean up crew? Snails/hermits? What about mini stars and clams? Are there any DSB safe starfish?

I guess are there sand grazers that are DSB safe? Or maybe the list of DSB safe life is a short list?

Thanks for the help!

Take a look at ipsf.com. They sell cuc that's just fine for DSBs.
You could get nassarius vibex snails, as they are scavengers, but nassarius obsoletus is a predator so you don't want that, for example. Herbivores are fine.

 

[TriggerThis]

Wow that's an amazing reef. My wife just looked over and was like "I want our reef to look like that!" Lol. So how is the maintenance ?

Thanks! I haven't done a water change in 5 months... And you DO NOT touch the sand. You don't siphon it or stir it or anything.
Think of the sand bed as being made of several layers. It has to be deep Bc at the very bottom where there is very little oxygen is where the denitrifying bacteria live.
That is also why it's important to use only the super fine sugar fine sand. For the maximum density to block oxygen.
And the layers cannot be mixed, each inch has different micro organisms and bacteria. If you take a net handle and push it all the way to the bottom you will create a mass death in the layers and cause a hydrogen sulfate pocket.
Then if you disturb that, it will release that gas into the tank and kill everything.
But if left alone the bacteria will process the death over the course of a couple months and the gas will be gone and no longer a threat.
So don't mess with it!

 

[TriggerThis]

And as far as clean up crews. The nassarius and cerith snails are fine and good Bc they keep the top stirred a bit and serpent stars and lenkias are fine. All grazing snails are fine. And hermits

And finally I would strongly urge you to start the DSB with nothing but the carribsea straight from the ocean live sand. This will give you all the right bacteria and animals from the start to keep the sand healthy. If you start with dry sand there's nothing in the tank to keep it healthy or anything and it will go downhill quick.

 

[vlangel]

I think you've been given bad information. Of course, the bacteria will repopulate. Don't fix something that's not broke.

Do you have lots of algae growth on your sand bed? No? Then it is working to reduce nitrates.

Thanks, that was my gut feel about it because the tank is running so well, but I don't know all the science behind a DSB.

 

[vlangel]

Nah, you were given bad info. Your bacteria is okay. You can ruin it by adding too much sand at once, but 1/4" to 1/2" should be fine. The thing is to avoid smothering the infauna that makes the sandbed work, but it doesn't sound like you did that.

I knew you could smother the aerobic bacteria on the surface so I even mixed the top eighth inch or so with the new sand. Thanks for answering my question.

 

[reefwatcher]

I have had a SSB in my 60 cube and I'm going to buy 2bags of sand and add it slowly a hand full every 3 or 4 days

 

[TriggerThis]

You'll need way more than two for a 60 gal

 

[JHuneke]

I've recently ( 2 months ago) upgraded and decided on a 5-6 in DSB ( new dry special grade sand). Had added all the critters I've been advised to, to INCLUDE 2 sand sifting stars ( in a 48x 18 x 6" DSB) I'm gathering here that was not a good move? Should I remove these guys now?

 

[TriggerThis]

Yes and you shouldn't have started with dry sand. The star fish are making worse

 

[Eienna]

I've recently ( 2 months ago) upgraded and decided on a 5-6 in DSB ( new dry special grade sand). Had added all the critters I've been advised to, to INCLUDE 2 sand sifting stars ( in a 48x 18 x 6" DSB) I'm gathering here that was not a good move? Should I remove these guys now?

Yes, remove the stars. They consume the other essential small animals.
Mini brittle stars are a better alternative.

 

[Mike J.]

I have had a SSB in my 60 cube and I'm going to buy 2bags of sand and add it slowly a hand full every 3 or 4 days

A good way to add sand to an existing sand bed is to gently push existing sand over making 6"x6" places with no sand and fill those with sand like this:

Putting Sand in an existing tank. - YouTube

 

[JHuneke]

Ok.. Didn't mention it, and not sure it matters, but I did add about the first inch on top of live established sand from my previous setup ( along with all my est live rock as well) which was a 2-3 in sand bed..well I'll be removing the ss stars tonight then.. Thank you

Yes and you shouldn't have started with dry sand. The star fish are making worse

 

[Whys Alives]

I was very pleased to have a functional DSB for over 5 years, but then had to move. That was very recently and I have to say I was also very pleased with the apparent health of the DSB when I finally tossed it out, so as to move the tank. Here is something I produced on RC back in the day. Enjoy!

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Deep Sand Bed -- Anatomy & Terminology

A deep sand bed, or DSB for short, can be a useful addition to a saltwater aquarium, refugium, or even a remote bin. Tho based on a remarkably simple idea, DSB discussions can become enormously complex. The purpose of this article is to offer a generalized understanding of the core concepts and specific terminology. This is by no means the final word on the DSB, nor does it advocate anything more than educating the reader, but it can also serve as a guide to a more serious investigation.

There are several potential benefits and possible drawbacks to having a DSB. Most often their purpose is for nitrate reduction, so that is this article's focus, but that is not their only purpose, nor is a DSB the only means for achieving that goal. Not everyone uses a DSB and many have tried them with poor results. Some do use a DSB and have reported good results for a decade or more. There is substantial disagreement as to why some succeed and others fail. Over the years, some general rules of thumb have evolved, but they should not be mistaken for definitive science. It is up to the reader to reach their own conclusions.

To better understand the anatomy of a deep sand bed, let us first look at a shallow sand bed, or SSB for short.

- Oxic: oxygenated.
- Aerobic: requires oxygen to function.
- Nitrifying: converts ammonia into nitrate.

In all aquariums, decomposition is largely performed by bacteria, but the process can be facilitated by the presence of a "clean up crew", or CUC for short. Detritus (waste) and other organic matter is first eaten by the CUC of crabs, stars, hermits, and snails. The smaller particulates they produce are then further broken down by copepods, other benthic organisms, and worms. The remaining dissolved organics are then converted by the "nitrifying" bacteria, from ammonia (toxic), to nitrite (less toxic), to nitrate (least toxic). All of this takes place within a layer of sand oxygenated by moving water, termed oxic, and the bacteria there require oxygen to function, termed aerobic. In a shallow sand bed this is where the process ends. The nitrate simply accumulates in the water column to be removed by ritual water change.

In a deep sand bed, there are another type of bacteria, termed anaerobic, that require a depleted oxygen environment to function. Among these are the "denitrifying" bacteria that convert toxic nitrate into nitrogen (which is mostly inert). The primary objective of a DSB is to provide a layer of very low oxygen, termed hypoxic, where bacteria can function anaerobically. The potential harm is in creating a layer completely devoid of oxygen, termed anoxic, where "reducing" bacteria can convert sulfate into hydrogen sulfide (rotten egg smell). This and other toxins can dangerously accumulate in a sand bed that is too deep or not properly maintained.

The prevailing wisdom is that the worms and benthic organisms are vital to maintaining a healthy DSB. In addition to cleaning the sand, it is believed their gentle agitation of the bed helps deliver nutrients to the bacteria while preventing truly anoxic conditions.

- Benthic: surface and near sub-surface sand bed layer.
- Hypoxic: low oxygen.
- Anoxic: no oxygen.
- Anaerobic: requires depleted oxygen to function.
- Denitrifying: converts nitrate into nitrogen.

The full benefits and challenges surrounding deep sand beds are still a matter of some debate, so it is important to point out that the conversation is often confused by competing terminology. Environmental scientists often borrow the term anoxic (labeled in blue) to mean extremely hypoxic, and anaerobic (labeled in blue) to mean truly anoxic.

Here are some general rules of thumb for maintaining a DSB. It should be at least four inches deep but no more than six, consisting mostly of fine grains, sometimes called "oolite" or "sugar-fine". Keep the benthic and worm populations healthy by avoiding Sand-Sifting stars, most crabs, and limiting hermits. Occasionally rejuvenate these populations with fresh liverock or true livesand from a well established aquarium, as this may be key to long term success. The sand bed should only be disrupted very gently over time. Brittle and baby stars, as well as Nassarius and Cerith snails, provide a slow and beneficial agitation of the sand, but vacuuming should be performed with great care, if performed at all. Remember, a deep sand bed is a living thing that must be kept in careful balance.

General Rules of Thumb:
- 4" to 6"; fine-grain; do not disturb or disturb with care.
- Helpful: Brittle & baby stars, Nassarius & Cerith snails.
- Unhelpful: Sand-Sifting stars, most crabs, too many hermits.
- Rejuvenate benthic and worm populations for long term success.


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(Jun,2009) Author & Illustrator: Whys. The following credits, listed in alphabetical order, are for collaborative work only and should not be assumed as endorsements of this article. Technical contributions: capn_hylinur, fsn77, jenglish, MattL, tmz, WaterKeeper. Additional peer review: adtravels, Biologist, luther1200, jasonrp104, Nanook, rishma, Sisterlimonpot, thegrun, therealfatman.


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I've placed "Nitrifying", "Denitrifying" (or "Facultative"), and "Reducing" in quotes, because I believe these are the best words to use in order to prevent misunderstanding when discussing the DSB.

 

[Mike J.]

Welcome to Reef2Reef, Whys Alives. That's not an ordinary post for a first post. Welcome to the forum.

 

[DSP]

A good way to add sand to an existing sand bed is to gently push existing sand over making 6"x6" places with no sand and fill those with sand like this:

Putting Sand in an existing tank. - YouTube

I disagree with this, pushing an existing sand bed over and trapping living critters is not a good way to add more sand, Like mentioned above adding small amounts at a time Is the best way.

 

[Mike J.]

I disagree with this, pushing an existing sand bed over and trapping living critters is not a good way to add more sand, Like mentioned above adding small amounts at a time Is the best way.

That's why the small 6"x6" areas. Maybe you think I'm getting senile and don't know what I'm talking about? I digress.

 

[DSP]

That's why the small 6"x6" areas. Maybe you think I'm getting senile and don't know what I'm talking about? I digress.

Again not good info and not surprised at all from seeing your recent post.