December In-Box

The In-Box is a collection of letters that may be of interest to others. Any material may be submitted and printed here. Through the exchange of information we hope to better everyones understanding of current trends andlatest technology. Please feel free to send anything you think would be of interest to someone.

This months letters are a continuation of the exchange between Eric Borneman and Sam Gamble on their experiences with the sand bed set-ups.

Sam:

After being in Chicago, MACNA, and St. Lucia, I have a lot of unfinished business that I am getting around to. Please excuse the long delay in responding, but I kept putting off this letter because of the topic and the depth I knew it would entail.

REGARDING the very in depth coverage to my response to your article on sand systems in aquarium.net, I would like to clarify a few things.

I am sorry if I meant to suppose that I considered a sand bed to be exclusively anaerobic or anoxic. In fact, i am aware of the gradients and areas where such facultative conditions are present. I was using the fact that we assume that reduced oxygen levels are present in the plenum, although oxygen should be more present than in the depth of the sand bed, am I correct?

In any event, the plenum in my main tank is indeed secure. The organisms (astrea snail and aiptasia's were already present after I had dropped in the eggcrate, added the screen and sand, etc. I was too lazy to undo the reef to rescue the snail, and I wanted the aiptasias to die anyway. They showed no zooxanthellic pigmentation while in the plenum, and there was no light underneath except what was transmitted vertically through the glass itself...unless we tint the glass black, there would be no way to avoid this internal conductance of light, which to the eye is not even present. This is the light source they began migrating towards. There is absolutely no way anything could dig into the plenum or escape from it...i.e. the cellar door to the basement is secured and has been. (Although I have a distinct pleasure to announce I have hundreds of tiny invertebrates that are now growing upside down off the screen in the plenum...they are unidentified, but resemble tiny filter feeding worms, perhaps? White with a stalk and tentacles (can't count the number...it really looks like pictures of deep benthic communities taken from thousands of feet down...they have obviously penetrated the pores in the screen from the sand...most fascinating!)

You proposed that the astrea present was due to penetration of the plenum and the presence of molecular flux that allowed for autotrophic nutrition. This was not the case...the snail, present by accident in the original plenum set-up, died, and I suspect from a lack of food. My point was that the length of time anemones and the snail survived before throwing in the towel from lack of light/food source may indicate that the environment in the plenum is less oxygen depleted than theorized due to sand depths that are not comparatively all that great. The amphipods were, I suppose, able to penetrate the screen while at a size that would allow them to do so. The screen, by the way, is even finer than that normally used, as I used the very fine mesh sun screen, and not the standard fiberglass which I have always thought to be to large in hole size. There is no settling of sand through the screen, and only in significant amount of the finest consistency particulate matter has settled on the bottom. Clearly, if you trust that my plenum is, in fact, completely sealed by sand and screen, covered by a minimum of 4 inches of sand, and has no "light source, then one would have expected the aiptasias and the astrea to have died sooner based on respiratory failure in that zone, wouldn't you? I certainly did.

I am glad you agree about the importance of high quality sand, though. Too many people are throwing a couple of inches of CaribSea on some eggcrate in unestablished tanks with no idea of biologic and biochemical processes and then wonder why no "Jaubert miracles" happen. I am also just about fed up with people thinking they have Jaubert tank just because they threw some substrate down. This is a hotbed right now, and I have to deal with it every day. NNR is such a much better and more descriptive word to describe what you are talking about.

One more point in your letter:

You rightfully point out that microfauna isn't responsible for the actual recycling of wastes. Of course it isn't...it's bacteria. BUT, the progressive breakdown by microfauna such as worms, etc., allows for a faster degradation and denitrification by bacteria...hence the reason composters with worms present compost so much faster than if you just throw garbage and leaves in a pile. The previously mentioned CaribSea bed will work,especially given some time, but the sand bed can be more efficient if the proper conditions for maximum breakdown are present.

My point is that nnr systems are very effective and wonderful. Like you point out, it is a complex series of reactions and processes that allow for its success in the aquarium. But, like the compost pile and the reef aquarium, conditions should be present to maximize its usefulness. This includes a proper depth, proper management by microfauna and larger organisms, establishment of denitrification zones, and on and on and on. I just wanted to let you know that I have been using these nnr systems for quite awhile, in several variations, and have noted remarkable differences between them and just wanted to hear your feedback of my findings regarding the snail and anemones now that you know some more facts.

Response:

Hi Eric, good to hear from you,

>> I am sorry if I meant to suppose that I considered a sand bed to be exclusively anaerobic or anoxic. In fact, I am aware of the gradients and areas where such facultative conditions are present. I was using the fact that we assume that reduced oxygen levels are present in the plenum, although oxygen should be more present than in the depth of the sand bed, am I correct? <<

Your more detailed illustration of the plenum is most definitely, most fascinating! I am happy to hear the cellar door was closed and the migration of meiofana (the in between micro and macro). If you ever break down the tank, I would be very interested in looking at a preserved sample. Also, there is a group of microbes called chemoautotrophs that may be present in your plenum (?). They could explain some of the observations you have. Whereas they require light it's of reduced quantity and they have been mostly associated with the oxic -anoxic interface. An important characteristic is the ability to catalyze the oxidation of reduced sulfur. Thereby, avoiding the toxicity that would prohibit meiofana, Truely interesting.

The respiratory failure would have come much sooner for the plenum invaders, if there had been a sizable load at cure time or when they decided to live (by introduction or invasion) in the lowest zones of the sand bed system.

The plenum usually can drop to near zero DO when there is increased microbial respiration above it. The metabolizing microbes use most of the available oxygen, whether it be elemental or diffused biosphere. Would like to know if you may have had chemoautotrophic colonies.

I avoid the term Jaubert Method like the plague. Couldn't agree with you more. The miracle system is nothing more than a home for a useable spectrum of bacterial ecology. AND,like in nature it varies greatly. Also, I want to impress on folks that the biofilm to algal mat succession is a natural occurrence and possible whenever the necessary ingredients are present; nutrients, substrate, and strong light. Hard to get around in a reef tank; sand or not. Better energy cycling is a big factor here, not just throwing in the magic sand. If you can find the author, Rysard Chrost, he's worth reading to help influence the "Jaubert Evangelists". One point I like; "The heterotrophic microorganisms are the key level at which the metabolism of the whole ecosystem is affected, i.e. nutrient cycling, organic matter transformation and mineralization, and energy flow. The measurement of microbial activity in natural waters is very important for understanding the dynamic aspects of the functioning of the whole ecosystem". We have to go beyond the NNR concept even. I try to sneak this type of concept into my next Cyber article. It will hopefully be understood when related to the Generic sand system. Believe it or not I'm trying to turn the "Jaubert" stampede towards energy cycling. Ain't going to be easy with some of the evangelists. Point well taken about the microfauna, although in some cases it includes microbes.. They are, for the most part, a side loop to the bacterial metabolisms. The actual majority of metabolism by bacteria (microbes) is by heterotrophs. Derived from this, on an elemental scale, a very important relationship is the carbon and nitrogen cycles. The role of sulfur surprisingly plays a crucial and interesting part in the flux of carbon to and from these cycles. Carbon dioxide is a certain source, but, bacterial sulfate reduction is a key. Bacterial sulfate reduction with the release of the end product hydrogen sulfide becomes a significant process in organic degradation at low redox potential. As a result, its contribution to total anaerobic minerlization can be considerable. Since two moles of organic carbon are respired for every mole

of sulfate reduced, sulfate reduction consumes large amounts of carbon. This is by far the major sink for organic carbon. Interestingly, denitrification appears to be a very minor sink or carbon. Here's another interesting relationship about carbon that "may" help explain some of your observations - During sulfate reduction, energy flow is decoupled from carbon cycling. Approximately 75% of the energy content of the organic matter which is decomposed is transferred and stored in hydrogen sulfide. When the sulfide and other reduced sulfur compounds are later oxidized, this energy is released. If the oxidation is merely a chemical one, the energy of oxidation is dissipated into the environment, However, many bacteria can catalyze the oxidation of reduced sulfur, either to detoxify the sulfide or to gain energy. A variety of chemoautotrophic bacteria can capture the energy of sulfur oxidations using oxygen or nitrates as the oxidant, and use the energy to fix carbon dioxide. In the process these bacteria produce new organic matter from carbon dioxide fixation. Food for plenum thoughts . . . Just suppose, that, denitrification produced a little oxygen, but resulted in little essential carbon. Chemoautotrohs used the NNR oxygen for sulfur oxidations to utilize more carbon for fixation and the production of organic matter, supporting life in an environment of just minimal light. Hmm.

Thanks for the letter. Great. TTYL Sam