Things to consider when deciding on the sandbed

[xerophyte_nyc]

This topic comes up many times, I wanted to get a good conversation going with talking points designed to help people make a decision. This is not about what is right or what is best. Let's discuss pros and cons and other factors.

 

Please feel free to agree or disagree, and tell us why.

 

Some Assumptions (Could Be Myths or Facts):

• A sandbed can be functional (nitrogen processing) or decorative/ non-functional.
• A sandbed can be deep (3-4+ inches in uniform depth) or shallow (1 inch or less)
• The top one inch or so of a sandbed is considered to be photosynthetic (EDIT)
• The anaerobic sandbed area can process nitrogenous waste.
• Larger particle sizes tend to trap more detritus and necessitate more maintenance, but may be easier to stir up and vacuum.
• Sand color does not seem to have any impact on a reef other than esthetics.
• Aragonite sand probably does not contribute anything significant to the tank's calcium unless pH is very low.

Functional Deep Sand Bed: (DSB) Without getting into too much detail, a functional deep sand bed is a concept whereby the reef tank is filled with 3-4+ inches of super fine oolithic sand. The goal is to create a pathway whereby nitrogen wastes are consumed by anaerobic bacteria in the deeper layers. The sandbed needs to be constantly "stirred", a feat accomplished by microfauna and sandbed friendly animals.

 

Maintaining a Functional Deep Sand Bed: Here is where things get dicey. It is questionable whether or not a DSB can cause the tank to crash. Proponents claim that the sandbed fauna has to be properly maintained for a DSB to thrive. The aquarist is not supposed to disturb the bed or clean it. Certain creatures are said to not be DSB safe, like crabs, sifting stars, etc.

 

If a DSB is desired, for whatever reason, it is the aquarist's responsibility to research this methodology. But I think it is safe to say that if you're unable or unwilling to make the effort necessary to maintain a DSB in the display tank, this is NOT a good option.

 

A shallow sandbed affords the aquarist the ability to more easily clean and maintain the sand without fear of disturbing the microbiology. Larger grain sizes trap detritus but are arguably easier to clean. Certain fish and inverts work well with a shallow sandbed because they can disturb it without fear of harming the tank. Regular maintenance is important so that detritus does not get trapped and cause problems.

 

The real tricky thing, to me, is a sandbeds that is neither shallow nor deep. Here is where aquarists may get into trouble, as there are more factors to consider. Is it OK to disturb, vacuum or stir-up a sandbed that is 2-3 inches deep? What about the anaerobic bacteria? What happens if I don't maintain it well enough and debris gets trapped and starts to decompose in the anaerobic zones?

 

In my mind, the decision is rather simple. If you don't want a bare-bottom tank, but do want the esthetic or functional appeal of a sandbed, then either go for a DSB and make sure you have full disclosure of all of the work needed...or go for a shallow sand bed with coarse sand for easier maintenance.

 

Discuss.

[Javious]

While I believe in the science of the DSB, I doubt the practicality of one in a nano tank. I haven't seen any research that can quantify the benefits. In a standard 10 gallon tank a 3 inch sand bed takes up 25% of the water column. Would the system be healthier with a DSB or with another 2 gallons of water? Another consideration would be the area, does it affect DSB functionality? I haven't seen this reported either. At this time I will stick with my decorative sand bed and the larger water volume it gives me.

[xerophyte_nyc]

There are a number of statements under the "some facts" heading that are simply not true. Where is the research that backs up your "facts"?

 

Good. My intention was to improve and correct the "facts".

 

Edit: Specifically, according to Richard Harker, aerobic and anerobic bacteria exist side by side in a sand bed rather than at different depths and all areas of the sandbed were able to process nitrites and nitrates. Different particle sizes appeared to be equally effective as a sand bed substrate.

 

Smaller particles have a greater surface area for bacterial colonization, so how are different particle sizes equally effective?

 

 

 

A "deep" sandbed is still just a sandbed and functions the same as any other sandbed. There really isn't any difference between a "deep" sandbed and a shallow sand bed, except the additional sand.

For purposes of aquariums, a "deep" sand bed I think would be more likely to develop anoxic zones simply because access for stirring/ cleaning is difficult. In the ocean, there are other factors of course.

 

This isn't true. See information above. This used to be speculation because no one ever did any research, but these things seem to be repeated as "facts" over and over even after the research has been done to dispel the myths.

 

You are right, I got mixed up. What I meant to say was the top 1 inch or so can harbor photosynthetic life because light can penetrate at that depth, not that it is oxygenated.

[slickwill613]

If it were a vote I'm gonna say finer grain and less than 1".

 

Anything else is just too much maintenance for me.

[xerophyte_nyc]

While I believe in the science of the DSB, I doubt the practicality of one in a nano tank. I haven't seen any research that can quantify the benefits. In a standard 10 gallon tank a 3 inch sand bed takes up 25% of the water column. Would the system be healthier with a DSB or with another 2 gallons of water? Another consideration would be the area, does it affect DSB functionality? I haven't seen this reported either.

Excellent. Where is the point where increased sand volume comes at the expense of water volume? And yes, area does impact DSB functionality.

 

 

At this time I will stick with my decorative sand bed and the larger water volume it gives me.

I think a decorative, relatively shallow sand bed would probably suit the majority of reefers.

[Javious]

After a little googling and math, I found out that a gallon of water takes up 230.4 cubic inches. In a BC29 a 3 inch sand bed will cost you 5.5 gallons of water, about 1/4 of it's actual capacity. In a 4' x 1' tank a 3 inch sand bed will consume 7.5 gallons, about 1/7 of the volume of a 55 gallon tank. The 20 long is a popular tank, a 3 inch sand bed would take the place of 4.7 gallons of water, very close to 1/4 total volume. For me this indicates that anything smaller than a 48 x 12 tank would be better served by having the water versus a DSB.

 

Just my opinion and the numbers are close but by no means 100% accurate, solely for discussions sake.

[xerophyte_nyc]

According to the study, larger particles tended to have irregular surface patterns that provided additional area, which made up for generally smaller surface area (per volume) that one would expect from the larger particles.

 

Interesting piece of info.

 

It's not even clear that anoxic zones are beneficial, so I'm not sure why one would care whether they exist in your sandbed or not since the anaerobic and aerobic bacteria exist in all areas of the sandbed and are able to complete the nitrogen cycle in the same manner. Also, the research found that areas of the sand bed that are oxic, suboxic, or anoxic can change quickly aren't dependent on the depth of the substrate. (as I noted above).

 

Anoxic areas are not necessarily beneficial. In an aquarium, it could be harmful. Hydrogen sulfide can build-up as a result of anaerobic decomposition. Dead spots in a sandbed are certainly a possibility in an aquarium if there is inadequate gas/ water exchange. It would seem this is more likely in a deeper portion of a sandbed, as well as other dead spots in a tank like under rockwork. Then if the sandbed is disturbed it could release the gas, even though there is unlikely to be toxic amounts.

 

 

Aurgh. I've yet to see anything that even remotely indicates that this is true.

This has been discussed in Ron Shimek's forum. In a reef tank, population dynamics make it difficult to maintain a diverse fauna where sand volume is limiting. This is of no consequence in a remote DSB.

[scribbles]

I have always run intermediate sand beds with a mixture of sugar and one size up sand. 1.5-2.25" in depth. Easy to maintain and as long as proper sand crew is kept, I have had healthy sand and tank parameters.

 

 

Exactly what you say is wrong to do.

[xerophyte_nyc]

Easy to maintain and as long as proper sand crew is kept, I have had healthy sand and tank parameters.

 

Easy...as long as proper sand crew is kept...

 

Exactly what you say is wrong to do.

 

I did not say that.

[xerophyte_nyc]

I don't really see that, but I do see where he says it's easy to just recharge the smaller sandbeds if their diversity begins to decline:

 

His forum is here: http://forum.marinedepot.com/Forum11-1.aspx, what you are quoting is an excerpt from an article of his. You'd have to do a search to find where it was discussed, I don't have the links at the moment. They even bantered about the idea that having rock sit on top of a DSB limits its ability to process nutrients because water flow is blocked. Most nano tanks may not be suitable for a DSB, long term.

[xerophyte_nyc]

The fact that some guy bantered about the possibility that live rocks on top of deep sandbeds may prevent them from functioning well doesn't provide a basis for sweeping statement like this.

Whether you choose to believe in the merits of a DSB or not, Dr. Shimek is one of the world's foremost experts on DSB for the aquarium and as recently as last year had a big article in Coral Mag. Those were his words of advice, not mine. The bantering was about other related things, but the concept of population dynamics in a limited sand volume was Dr, Shimek's take. He is a marine biologist and although everything he studies and writes about may not be transferable to an aquarium or even be totally correct or repeatable, but I do believe him to be as reliable a source of hobby-related material as any.

 

I will try and find that thread on his forum for you, but it might take some time since that forum can be difficult to navigate.

[dmarkham]

Ok here are my thoughts from what I have seen and what I have understood throught the years of being in this hobby.....

DSB have a purpose if used correctly in a large system. As far as a nano they are a waste of space IMO. The idea is the same with Live rock. You can effectively break down waste and support a system with larger pieces of live rock over rubble. Rubble offers more surface contact, but the larger peices offer the ability to break down waste entirely though the cycle. This is why live rock is better then bio balls. A deep sand bed need to be 4" plus to be effective. You do not mess with it and again I have only seen this work in large syatems. There is a LFS by my that runs a DSB in a display tank with great success. They also do not use a sump or a skimmer on this system. It has been running for over five years that way. Also this has came up on RC a number of times. the debate is better left there.

 

Again this is not something I would do or feel you should do in a nano tank. Again this is IMO. You can find studdies to support both sides if you look hard enought on the web. It comes down to is it the right thing for your tank?

[Nano sapiens]

One needs to be careful when one starts to proclaim 'facts'. You'll need lots of credible, supporting documentation to back it up. Also, beware of the so called 'Experts' who rely on theory, not controlled and repeatable experiments, to validate their claims.

 

In the real world, a study based on a large sampling of Nano tanks should give a good indication of what type(s) of SBs have been successful and most importantly, how the SBs were treated/maintained. There are a lot of variables to this equation, however, any of which could determine the level of success. And, you also need to quantify what 'successful' means so that everyone understands the criteria.

 

If you are really interested, you could start a poll where people can answer a few relevant questions.

[dmarkham]

I read Shimek's "big" two page article in coral magazine (Link here). In fact, he mentions that as recently as a year ago he used to believe that the fauna in sandbeds died out because of the limits of our enclosed system (and presumably smaller systems would have additional limits), but he now says that you just have to feed the sand bed to establish the correct populations and allow them to repopulate, so I suspect that any "banter" that you may have seen on his thread is just that. But, this again brings up the problem. People like Shimek aren't doing studies. He's making recommendations based on his opinion. He made the recommendation that I cited above based on his opinion at the time that you need to add sandbed critters to your tank every year to maintain populations and then less than a year later, he completely changed his opinion and neither time was it based on fact. It would be easy for Shimek to do a study and find out if feeding a sandbed actually worked to maintain the populations of critters that we need, but he hasn't. He's making recommendations based on a hunch and then presenting it to the aquarium community as fact. It's not. Now others are regurgitating his opinions and presenting them to everyone else as if they are facts when they were never facts to begin with.

 

 

 

Then, where are these studies that compared a 3" deep sand bed and a 4" deep sand bed and found the 3" deep sandbed to be ineffective? I ask because I have never seen one although I have seen many showing the exact opposite. I mostly see this type of statement repeated as fact when it is just based on outdated and incorrect information.

 

 

 

I guess you did not see the IMO statement. I am not a biologist as I assume you are not either. There are case studdies to support both sides. I agree with Nano sapiens in the fact that there are too many variables. I am not trying to disclaim what you are saying or trying to be an A@# or anything. You say outdated information, but I tend to disagree, But again IMO only. With that I am out of this convo.

[Sea_Of_Treachery]

its a wrap

[markalot]

DSB's can start lots of debates, but regardless of who said what and when and what their credentials are ....

 

Where oh where do the phosphates go?

 

I'm a believer that sandbeds can function ok for (1 year * depth.). This best explains while there were so many proponents of 6 inch DSB's for about 6 years or so.

 

Lastly, a scientist proclaiming something does NOT make it science. I challenge you to find a real independent case study to support filtration. Too many false authorities in this hobby makes for a very interesting ride.

 

The number one rule most people don't follow:

 

Do what you think works best, and when it fails tell us about it. This is how we learn. Too often people preach their methods work best and then go silent.

 

I, for one, have no idea what works best.

 

I'm wondering if DSB was proposed out of fear people would quit the hobby knowing there is no way to export some nutrients from the sandbed. Freshwater uses plant roots to do the export, but there is nothing like that easily available for saltwater. The only real solution, in my opinion, is to understand a sandbed has a life and plan to replace it over time.

 

/shrug

[ajayjack]

I would disagree with this one:

 

"Sand color does not seem to have any impact on a reef other than esthetics."

 

White sand bed will reflect more light back up at corals. Black will obviously absorb and not reflect.

[scribbles]

DSB's can start lots of debates, but regardless of who said what and when and what their credentials are ....

 

Where oh where do the phosphates go?

 

I'm a believer that sandbeds can function ok for (1 year * depth.). This best explains while there were so many proponents of 6 inch DSB's for about 6 years or so.

 

Lastly, a scientist proclaiming something does NOT make it science. I challenge you to find a real independent case study to support filtration. Too many false authorities in this hobby makes for a very interesting ride.

 

The number one rule most people don't follow:

 

Do what you think works best, and when it fails tell us about it. This is how we learn. Too often people preach their methods work best and then go silent.

 

I, for one, have no idea what works best.

 

I'm wondering if DSB was proposed out of fear people would quit the hobby knowing there is no way to export some nutrients from the sandbed. Freshwater uses plant roots to do the export, but there is nothing like that easily available for saltwater. The only real solution, in my opinion, is to understand a sandbed has a life and plan to replace it over time.

 

/shrug

I wholly agree with this, IMO, sand beds have a live span of 2.5-3.5 years. I run 2” sand beds easy to maintain and not too expensive to replace.

 

 

I have always noticed a significant increase in tank health after a very old sand bed is changed. For that reason I cycle about 1/2 of mine a year. I have replaced 100% of the sand in the tanks I have helped saved many times, all too great effect.

 

 

First thing I do when asked to help save/restore old neglected tanks, is change the heater, remove and replace 100% of the water and sand bed, as well as shake the hell out of the live rock in salt water. Always a night and day difference in a very short amount of time.

[Nano sapiens]

The only real solution, in my opinion, is to understand a sandbed has a life and plan to replace it over time.

 

/shrug

 

This is one solution to the SB question. In essence, one is starting over with a clean SB that doesn't have detritus buildup.

 

I have ~1" SB in my Nano that is original and over 4-1/2 years old, which I vacuum every week. The tank is in what I consider good health (thriving corals, minimal algae, etc.). I intend to continue with this SB as long as I have the tank running. I have consistent '0' PO4 and no NO3, per Salifert test kits, and that's with no chemical or mechanical filtration other than LR and LS. What I have noted and experienced is that problems develop when a SB is left undisturbed for an extended period of time. The buildup of detritus is the main issue, IMO. Not only is it a source of contaminants, but on a mechanical level, it impedes effective flow and oxygenation to the bacteria which are essential to the nitrification/denitrification process.

[penfold2]

I think there is some debate as to what constitutes a functional sandbed. The AA articles linked above suggest that just about any sandbed can have an effect on nutrient levels. However, they really didn't test the type of sandbed suggested by Dr. Shimek. His idea of a "functioning" sandbed is one with a thriving population of infauna. He has stated that a properly constructed sandbed practically vibrates from the combined movements of the infauna. But these organisms have very specific requirements in terms of particle size/depth and available footprint. And obstructions like rocks can significantly reduce the available footprint, since many organisms will not populate areas within a certain distance of a solid edge. I believe his recommendation is a sandbed with an average particle size of 0.1 to 0.25 mm and a footprint of at least 6-10 square feet in order to maintain healthy infauna populations. His recommendations come from sample population measurements done on his own tanks as well as sediments in nature. A sandbed like this may function on a completely different level than a typical sandbed. Nutrient levels may be practically non-existent instead of simply reduced. Massive amounts of plankton can also be produced from these beds.

 

Personally, I will stick to shallow, coarse sandbeds that can easily be vacuumed during water changes, since my tanks tend to be on the smaller side. But there are examples of tanks that have had excellent results with "live" sandbeds, some utilizing few, if any, water changes over many years. I've seen enough of these examples to believe that there could be a significant difference in the functionality and benefit of these sandbeds.

[xerophyte_nyc]

An Experimental Comparison of Sandbed and Plenum-Based Systems. Part 1: http://www.advancedaquarist.com/2005/6/aafeature Part 2: http://www.advancedaquarist.com/2005/7/aafeature If you want the summary: plenum based systems are less desirable and had higher mortality rates. Not much difference between deep sand bed and shallow sand bed. Deep coarse sediment designs had the lowest mortality rate. The experiments were done in nano sized tanks and are directly related to most of our aquariums.

There are some interesting trends worth noting in these 2 studies. For example, phosphates and nitrates are lower in deep fine sediments, and shallow coarse. Water flow might have a significant impact on shallow beds. So many variables.

 

A seemingly growing, more or less "trend", in the hobby is understanding there is much more food on a reef than previously thought, and some are trying to duplicate this in aquaria. That of course is challenging because our ability to export nutrients is limited, compared to a natural reef.

 

I would love to see some experimental designs where there is more food being offered to the aquarium, including phytoplankton and small particles, which support the life on the lower levels of the food chain. I think that this approach could favor a DSB. Minimal feeding may not show much difference among different sandbed systems, but maybe a higher food input may bear out measurable differences. Who knows?

 

In my own tank, I am trending in this same direction by using a DSB and an algae scrubber. I don't have nearly enough experience to make any real judgments or recommendations. All I can offer personally are snapshots in time of what is going on.

 

My goal with starting this thread was to come up with some guidelines to help people decide how to design their tank's sandbed since it is a frequent query. Instead it somehow turned into DSB debate even though, at least I don't think I did, ever make a clear recommendation that a DSB is a better option. I am trying to figure out what, if any, factors could make a sandbed easier to maintain and therefore may be more suited for a beginner just starting to set things up. I still think that a shallow sandbed with coarse sediments makes a good fit.

 

Makes for a lively, sometimes contentious and emotional discussion, that's for sure.

[penfold2]

And of course, this actually isn't what Shimek said at all.

 

If you read his recommendations, he suggests exactly what I wrote above. He did achieve a healthy DSB in his 45g, but he also stated that it took a lot of careful observation and frequent maintenance. Most people are not going to devote that much time and energy to their sandbed, so he suggests much larger footprints which are inherently more stable. If you ask him about adding a DSB to a 3 square foot tank, he will tell you it is not a good idea.

 

I will be curious to see how xerophyte's sandbed does since he seems like the type that will do the proper research and preparation. I have been tempted to try it, but it would be a pretty big inconvenience to have to remove a DSB from a display tank if it didn't work out.

[markalot]

Well, the

 

Like this?

 

An Experimental Comparison of Sandbed and Plenum-Based Systems.

 

Part 1: http://www.advancedaquarist.com/2005/6/aafeature'>http://www.advancedaquarist.com/2005/6/aafeature

Part 2: http://www.advancedaquarist.com/2005/7/aafeature'>http://www.advancedaquarist.com/2005/7/aafeature

 

If you want the summary: plenum based systems are less desirable and had higher mortality rates. Not much difference between deep sand bed and shallow sand bed. Deep coarse sediment designs had the lowest mortality rate.

 

The experiments were done in nano sized tanks and are directly related to most of our aquariums.

 

Unfortunately no, I would not call that a scientific experiment. There are a lot of examples of those kinds of "experiments" done by the hobby-scientist and referencing other hobby-scientists.

 

Doesn't mean it's not useful, but there is no real control. I'll re-read to make sure I didn't miss anything, but my opinion is the experiment is too short and I fail to see a real control that would demonstrate that any conclusions, like that puffer living longer, were not random events.

[penfold2]

If you want to have him write a letter clarifying his current position, then I'll stand corrected, but really it looks to me like you are just making stuff up and trying to attribute it to the recommendations of Shimek, when it simply isn't. There's too much of this misinformation in the hobby and I really just don't understand what people think it accomplishes.

 

I am not making anything up, and I'm certainly not going to ask him to write a letter. These points have all been made numerous times on his discussion forum. Here are just a couple of links I quickly gathered if you care to read up on it.

 

http://forum.marinedepot.com/Topic50341.aspx

 

http://forum.marinedepot.com/Topic112543.aspx

 

One quote in particular regarding the "halo effect":

 

Many marine animals form their population patches with regard to materials in the sediments, and often the animals stay away from large items. In aquaria, large items are "aquarium walls," among other things (like embedded live rock). These patch dynamics mean that there is a halo-effect around the edges of an aquarium where many animals will not preferentially live. You can think of a sand bed in an aquarium as square donut hole with the donut being the edge-affected area. When a tank gets below the foot print of about a typically 40 gallon tank, there simply is not enough sediment surface area, nor volume that is present to accomodate a viable sand bed critter population array.

[Nano sapiens]

^^...correct.

 

Due to the small size of our Nano systems, there will always be a very limited number of species and population of 'sand critters' compared to what exists in a natural setting. If the tank has carnivores, then even more so. From a practical standpoint, I am not concerned with the limited in fauna at all, only that the bacteria have a suitable environment in which to do their thing effectively.