I have returned from lurking in the shadows!
As I did so long ago, I'm going to sum up where
I think think we are. Before I do that, though, I must say a couple of things. I have spent a lot of time today preparing a 140 gallon freshwater setup to be converted to reef; it is 10PM; I am tired. Therefore, I don't really have the energy to give the proper people credit for their ideas. Please do not be offended if I am obviously referring to any posts that you made and I don't give you credit. Also, to the science people: the chance of me being in error concerning certain processes is very high this late at night. Please do not hesistate to correct such errors. I just ask that you do so gently
. Finally, I have added personal remarks in this format: {remark}. These remarks are intended only as food for thought. Many of them are marginally off-topic, and are not really intended to add to the discussion. They are my
opinions and should be read as such, not as scientific fact.
Onwards to the summing!
1. In case you are joining late and didn't see the initial posts,
well-cured live rock is very important. Whether you "cook" it
(and I still don't like that term; I think it's misleading as to what it does for the rocks) or use some other mode of curing is largely dependent on your specific goals. Using uncured live rock can allow the DSB to potentially become a nutrient sink (that
can happen, but is not guaranteed).
2. There is not quite a consensus on particle size. The study that was quoted somewhere on page 20 stated that the highest diversity comes from mixed sizes. What constitues mixed sizes, it did not say. {Based on my own [admittedly limited] reading and experience, particle size is important, but not something to worry yourself to death with. There is most certainly an optimum size range for maximum diversity. However, I have had many tanks that use beds of different particle size, even crushed coral, and have had good results. There is no doubt in my mind that those beds have nowhere near the diversity of nature, but it is enough diversity to accomplish the goals of filtration. But I digress; the goal of this thread is to "optimize sand beds", not to simply "come up with a sand bed that works OK."}
3. Composition: Very interesting thoughts here. It might turn out that silica is a better base than aragonite. As is usually the case in the hobby, each has its pros and cons. Some reasearch is definitely in order. {I prefer aragonite. The fact that I started with aragonite and have had success with it makes me more than a little biased. I have not used silica, so I cannot comment on it. I will have excellent opportunities for research over the coming semesters, and I will definitely look into it}
4. Infauna (be warned, though, that this section has a lot of opinion in it): Studies have shown that faunal extinctions often occur within two years in captive aquaria. As the fauna are a crucial part of the filtration in a sand bed, this is very significant. I think that many problems with DSB collapse are a result of fanual extinction. I have zero evidence to back that up; it's just me connecting the dots, so I could
very easily be wrong. So far, it looks like the only way to circumvent this problem is with recharge kits.
5. Phosphate: talk about the "great unknown." Actually, more properly, phosphate with relation to sand beds should be called the "great fuzzy." There is a great deal of information about the processes concerning phosphate. Phosphate will bind to things; that's in its nature. Eventually, binding areas will be taken up, and the phosphate will remain in the water column. There are, however, numerous ways to keep phosphate under control to slow the process. In the DSB, the fauna consume detritus before it can break down and release phosphate. Given the plethora of life in a sand bed, I am sure that there are also organisms that use phosphate is some way. However, one thing remains clear: no matter what happens,
phosphorous is phosphorous; it cannot change without nuclear decay. Unfortunately, unlike the case with nitrogen, no phosphate mechanism ends in free phosphorous leaving the aquarium. However, phosphourous is continually added to the aquarium. Therefore, you
must have a system of export. Agressive skimming is one good way, as is harvest of macroalgae. {Oh, and yes, the fact that macroalgae grows
does mean there is P in the water, albeit in very tiny concentrations. The hope is that the macroalgae is limited by the P, and thus removes it before it can get to harmful concentrations. Algae grows on the reef, too, it's just exported (by herbivores whose water-soluble waste leaves the area on currents) before it makes itself known.}
6. Good water flow helps increase the effectiveness of DSBs, primarily by keeping wastes in solution where they can be removed by export processes. Good water flow is also good for your corals, so adding flow should just help all around. The potential for sandstorms does exist, but that can be avoided with some good engineering, as well as by possibly layering some heavier particles over the fine ones, although that is currently under debate as to its effect on infauna. {Personally, I see no problem with coarser substrate, having had succes with coarse substrate. Again, though, this is the "optimization" thread, not the "OK" thread. Also, I have set up or maintained many sand beds that are in tanks with very high flow. There will be some sandstorms at first, but, like dunes on the beach, the bed will eventually reach a permanent, non-sandstorm, configuration.}
7. Finally, good all-around husbandry helps maintain the effectiveness of DSBs. Limiting the rate of phosphate import is crucial (ie don't overfeed), and coming up with a good nutrient export system is very important as well {keeping the skimmer clean and operating well is also a big part of this}. The DSB will only do what you set it up and maintain it to do. {One thing that I think is often overlooked is learning to "read" your tank and its inhabitants. They will tell you long before any test that something is going wrong. Also, by the time you read their warning signs, there is usually still ample time to act. With test kits, though, you might get readings only when its too late for prevention.}
8. The Rest of the Story. So far, what happens deep in the sand bed has not really been dealt with. This might be an area in which research is required, or the information might be floating around out there and no one's picked it up.
I'm going to close with my personal mantra. When in doubt, look to nature. Nature has been keeping reefs a lot longer and better than we have. Of course, at the same time, you also have to remember that nature wasn't doing it with a glass box.
