Deep Sand Bed -- Anatomy & Terminology

[Whys]

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 beneficial nitrogen. 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. Environmentalists 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.

[Whys]

The mods have seen fit to keep this an open thread, so I should warn potential posters of a couple of facts.

1.) This article comprises the full extent of my own knowledge on this subject. It intentionally generalizes certain nuanced facts and does not cover every aspect of the DSB.

2.) I can be testy and if your lucky I will recuse myself from the conversation. You've been warned.

[sruiz]

Good Stuff. Thanks for Sharing and breaking it down.

[Lyotim88]

i've heard that there's somewhere you can buy the worms and living creatures for a DSB. Is this true? Do you know where?

[Aquarist007]

well done----thanks for perserving with this project.

lyotime88----living in long island--you just need to go down to the ocean and scoop a nice big cup of that Manhattan Mud.
PaulB who also lives on LI swears by the stuff

[WaterKeeper]

But you also might invest in a detrivore kit. They are sold by several of our sponsors and have organisms a little more accustomed to reef temps than those off L.I.

[Aquarist007]

Originally posted by WaterKeeper
But you also might invest in a detrivore kit. They are sold by several of our sponsors and have organisms a little more accustomed to reef temps than those off L.I.

would these detrivore kits accomplish the same thing as the live Manhattan mud?

should also add that the simplest way is to get a cup or so of substrate from someones established refugium

[WaterKeeper]

Bacteria wise the mud from any SW area will seed a bed. The problem is the higher lifeforms don't adjust to temperature fluctuations as readily as do bacteria and most protists. The detrivore kits normally contain worms, pods and other sand shifters that are unique to the reef environment. Not to say some are not found in L.I. Sound but their hebetate is not the same as that of the reef.

[Aquarist007]

Originally posted by WaterKeeper
Bacteria wise the mud from any SW area will seed a bed. The problem is the higher lifeforms don't adjust to temperature fluctuations as readily as do bacteria and most protists. The detrivore kits normally contain worms, pods and other sand shifters that are unique to the reef environment. Not to say some are not found in L.I. Sound but their hebetate is not the same as that of the reef.

sorry I guess I should of asked if these detrivore kits would be the same as taking a cup or so of sand from a well established refugium.

[jenglish]

I believe most of the worms you will get out of a piece of LR as well. Inland Aquatics sells specific kits full of DSB friendly critters, I'm sure some of our sponsers do as well (IA is the only kit I have ever purchased).

[Whys]

Here is a valuable critique that was offered in the final review thread after this article was made sticky.

by KarlBob
I think the term you want here is "Environmental scientists", not "Environmentalists". Environmental scientists study the environment, conduct research, create computer models, etc. Based on the results of the studies, research, and models, environmentalists strive for personal and political action to benefit the environment. Although many environmental scientists are environmentalists, the vast majority of environmentalists are not environmental scientists. It's a picky, but often important distinction, especially to environmental scientists.

[Whys]

Originally posted by capn_hylinur
thanks for perserving with this project.

I'm a real peach to work with too!

BTW, that should read "persevering". "Preserving" is something you do with antiques like WaterKeeper and yourself.

At least I usually play well with others. Thanks for perserving with me.

[Aquarist007]

Originally posted by Whys
I'm a real peach to work with too!

BTW, that should read "persevering". "Preserving" is something you do with antiques like WaterKeeper and yourself.

At least I usually play well with others. Thanks for perserving with me.

preserving freudian slip dealing with WK, Tmz, PaulB and myself--we are all well preserved for our age.

[Sugar Magnolia]

FWIW, IPSF also sells sand bed critters. http://www.ipsf.com/ I've ordered from them before. The only thing I would steer clear of is the sand bed clams. They don't live very long.

Love the gnomes whys.

[WaterKeeper]

Paul and I have a problem, as our tanks are so old, we need Trilobites

to seed ours sand beds and they are really hard to find.

Adrienne,

Do you think that is one of the exotic vacations Travelocity has in mind?

[Whys]

WaterKeeper, it's not just you and Paul any longer. My aquarium software says it requires 1 trilobyte for installation.

[WaterKeeper]

[Aquarist007]

Originally posted by Whys
WaterKeeper, it's not just you and Paul any longer. My aquarium software says it requires 1 trilobyte for installation.

get the newer version

[Aquarist007]

Originally posted by WaterKeeper

Good to be back to frivolities

In case you missed the last question---jello gets messy at our age eh

sorry I guess I should of asked if these detrivore kits would be the same as taking a cup or so of sand from a well established refugium.

[Sisterlimonpot]

Fine work Whys,
I lost track of the project over the last couple weeks but reading this from the beginning really laid it out well, I know that future hobbyist will be able to make an informed decision on whether to choose a DSB or not.

Btw Love the gnomes

[Whys]

Originally posted by capn_hylinur
get the newer version

Seems over rated.

[tmz]

Nice job . Product condenses a lot of information in an understandable format.

[tmz]

I think it's important to note that nitrite labled(less toxic ) is really nothing to be concerned about in a salt water tank as a toxin. The label is technically accurate accurate but may benefit from the folllowing clarification.

While as an excess nutrient there is cause for concern, the large amount of chloride, 19000ppm ,in seawater neutralizes it's toxic effects. Many get caught up trying to test and manage for it in a qt tank for example(making qt management more difficult than it has to be) when it's not necessary. Many carry over freshwater fears of nitrite to salt water inappropriately. While there may be some level of toxicity when it hits hundreds of parts per million,this a level as a practical matter is not likely acheivable in a marine tank.

[Whys]

Thanks for the clarification, tmz. You've been invaluable to this project.

[WaterKeeper]

Did he supply the captive bred lawn gnomes?

Tom,

You might get a argument on nitrite toxicity from pro coral breeders. High levels have been shown to cause bleaching and other pathological changes of corals but it doesn't affect fish at the concentrations normally found in the marine aquarium.