How much live rock do you really need?

[cracker]

Chim...I do a major sand siphon, (detritus), every second water change or 3 months.

[cookie extreme]

Eons ago, about 1994 or 1995, when the reef aquarium hobby was in the dark days of its infancy, many aquarists did not bother to feed either their corals or any other animals with zooxanthellae. This rather silly (well – I could think of better adjectives, but "silly" works – and is not too impolite) practice was based on the idea that since these animals had photosynthetic endosymbiotic algae, they got all their necessary nutrition from those algae and did not need food. Food was considered a necessary evil; while necessary for fish, excess food polluted the tank and caused all sorts of problems. This was a time when the prevailing methodology for keeping reef aquaria advised a "bare bottom tank" which could be vacuumed clean of excess food and detritus on a daily basis.

About this time, a new way of keeping marine tanks, called the "Berliner system" became known to American aquarists. This methodology was more-or-less developed in Germany, hence the name "Berliner system," and involved keeping systems with an inch or two of fine sediment or sand on the bottom. One of the immediate results of using this system was that for the first time, it became easy for all aquarists to keep small-mouthed stony corals, such as Acropora, alive for extended periods. This success was generally attributed to the ability of a Berliner system to keep the mineral nutrients at low levels approximating those levels found on a natural reef. What most aquarists didn’t stop to realize was that this system for the first time provided a way for the reef aquarium to continually produce a source of food for those corals, and that this was why corals survived in such aquaria.

Coral Feeding – A Necessity

Until recently, most aquarists didn’t think they had to provide food for their corals and soft corals. The myth that corals get all of their necessary nutrition is really well entrenched in much of reef-aquarium reference "literature." That myth developed from a misunderstanding of the role of zooxanthellae, and a misinterpretation of coral physiological literature.

A bit of history is in order here. Corals have been known as being alive since antiquity, but just what kind of organism they were was not clear until fairly recently. Zooxanthellae were noticed in corals in the nineteenth century, but their role in coral physiology and nutrition was not clarified until the middle 1980’s. Initially, these algae were considered to be parasitic, and corals were presumed to be totally predatory. This was a view first elucidated clearly – and loudly - by the eminent coral research C. M. Yonge, in the 1930’s. Not much in the way of coral physiological research was done until the late 1960’s when a series of researchers began investigating zooxanthellae. A lot of these investigations were basic fundamental research asking questions on the order of, "What is this stuff?" and "What is doing inside the coral?"

These researchers rapidly came to the conclusion that corals were not totally predatory, but rather were symbiotic organisms, and that the zooxanthellae provided some essential nutrition to the coral animal. Subsequent work showed that for short periods, the zooxanthellae could provide all of the respiratory energy requirements for at least some corals, for periods up to a day. This conclusion, of course, got published in the scientific press, and made it into textbooks and, almost immediately, it was misinterpreted.

The problem comes from the phrase "respiratory energy needs." All animals respire, and on a cellular level, this means that they use oxygen, in this case oxygen dissolved in sea water, to break down sugar to carbon dioxide and water. The sum of this reaction can be written as C6H12O6 (= sugar) + 602 (= oxygen) à 6CO2 (= carbon dioxide) + 6H2O (= water) + Energy. Or, phrased differently, one sugar molecule, burned completely using six oxygen molecules, yields six carbon dioxide molecules and six water molecules, plus a whole lot of energy. In the coral’s cells, the sugar comes from the zooxanthellae, as they produce sugar by photosynthesis. Photosynthesis is basically the reverse of the reaction shown above; where light energy is used to fuse carbon dioxide and water to form sugar and oxygen. The coral cell uses the energy produced by the process of respiration to perform all of the work necessary to just stay alive. This work is called the basic metabolism of the coral cell.

Consequently, the bottom line is that corals don’t need any food to simply exist, provided the zooxanthellae are producing sugars by photosynthesis. Many early coral reef aquarium "authorities" seized on this fact like a pit bull on a postman, and said that corals don’t need to feed as their zooxanthellae do "it" all. Whatever "it" is...

And, they couldn’t have been more wrong.

While zooxanthellae provide nutrient to corals, they provide it only in the form of sugar, and while sugar can provide the energy for coral growth, it cannot provide the raw materials for coral growth. All animal tissue, and coral tissue is no exception, is made mostly of proteins, and proteins are made of amino acids. Each amino acid has, as its core, an amine or ammonia group built around a nitrogen atom.

All organisms can use sugars to provide the energy to utilize amino acids and to make or breakdown proteins, but the nitrogen for this process must come from some other source than photosynthesis. Zooxanthellae live inside coral cells, and are bathed in the cytoplasm or internal fluid of that cell. This fluid is rich in amino acids, and zooxanthellae can absorb, eat or incorporate those animal amino acids into themselves and use them to make proteins. These, in turn, may be used by the coral in part of its growth.

Aquarists often think that their corals produce a skeleton made of pure calcium carbonate, in the form of aragonite. This is not actually the case; the skeleton is actually formed of an organic matrix and calcium carbonate crystals deposited in two closely-linked phases. Initially, a fibrous proteinaceous matrix is laid down. Subsequently, the calcium carbonate is precipitated onto this matrix. There is some evidence that the precursor molecules of the organic matrix that is the basis for the coral skeleton are produced by the zooxanthellae. However, do note that the nitrogen for them must have come initially from the coral cell.

Thus, the question arises as to where the nitrogen in the coral cells comes from. There are two sources of this nitrogen. First, nitrogen may be available, dissolved in the water, as nitrate or ammonium ions. Although sea water is saturated with nitrogen gas from the atmosphere, only a few species of nitrogen fixing bacteria can convert it to useable form. Animals, such as corals, can not do this, and they either must rely on dissolved nitrates or ammonium or get their nitrogen from some other source. All corals appear to be able to absorb very small amounts of nitrogen containing compounds from the water, but these are insufficient to fulfill most metabolic requirements.

The second, and major, source of metabolic nitrogen for corals, sea anemones, and other zooxanthellate animals, comes from feeding, either on other animals or on particulate organic matter floating in the water. In either of these cases, the ingested food is rich in nitrogen. As I have already noted, animal tissues are mostly protein, and when an animal is killed and eaten, its tissues are reduced to their useable chemical constituents by the digestive process. These constituents are incorporated into the cells of the predator and used by that cell to produce more proteins. Only this time, they are components of the coral cell.

Particulate organic material is found in all natural sea water and is common in our aquarium waters as well. Often the particles are so small that they are not visible to the unaided eye. Such particles are small blobs of organic material, and they are covered with bacteria which are digesting them. Other such particles may simply be bacterial in origin. Bacteria are a very good source of useable nitrogen, as the bacterial cells have a higher ratio of nitrogen to carbon than do either plant or animal cells. The particles forming particulate organic material are often very small and most bacterioplankton are even smaller, so a couple of questions need to be asked. First, do corals actively feed on this material, and second is there enough of it in the normal water flowing over a reef to actually provide much nutrition on the reef. The answer to both questions is a resounding, "Yes."

The tiny polyps of this Porites, and their even tinier mouths are indications that much of the nitrogen necessary for this animal’s tissues come from microplankton.

Interestingly enough, much of the early work showing the importance of this material was done by Russian marine ecologists, particularly Yuri Sorokin. The work was published in Russian-language journals starting in the early 1980’s. Because this literature was not published in English, and because of the provinciality of many American researchers, particularly in the Cold-War years, it appeared simply to be ignored until about 1990 when translations became available. The disappearance of the Soviet Union in the early 1990’s also gave a boost to the acceptance of a lot of the research by Russian ecologists. Russia could no longer afford to support the research these scientists were doing and many of them went elsewhere to work, and started publishing in English language journals. Anyway, for whatever reason, the importance of small plankton started to become apparent and obvious to American ecologists around the middle part of the 1990s.

We now recognize several different categories of what may loosely be called microplankton. This is material that, by definition, is too small to be collected in the normal plankton collection devices used for either zooplankton or phytoplankton. It was simply missed by earlier workers; however, as more work is being done it has become apparent that microplankton provides a tremendous amount of food to coral reefs.

An old, but true, generalization of ecology, is that the size of the food gathering apparatus is correlated with the size of the food eaten. This is evident in the so-called small-polyped-stony corals. These animals are colonial and are made of many small individuals each with a tiny mouth. They form the dominant animals on reef faces and crests, the places that receive an almost continual bathing in this bath of microplankton. And they eat it. It is very difficult to actually get a handle on coral feeding, much of this microplankton is difficult to identify and rapidly digested, so that if a coral is collected for the purpose of examining what is in the gut, the gut contents may be digested beyond recognition between the time of collection and the time of preservation of the sample, even if this is only a few minutes. Nonetheless, research indicates that most of the microplankton hitting the reef corals is effectively removed from the water and ingested by these corals.

The fact that many of these corals grow very rapidly is testament to the availability of the appropriate food source. Without this food, they simply would not have the raw materials to build the tissues necessary for growth.

So… How can we provide such materials in our reef aquaria? Given the title of this essay, I will bet any reader will suspect the answer has something to do with sand beds.

That sand beds would be good producers of microplankton was alluded to earlier when I noted that even the shallow sand bed of the so-called "Berliner System" helped hobbyists keep previously unkeepable alive. Our reef aquaria are what a biologist might call "microcosms," or small copies of the real habitat. These contain the appropriate substrata, animals, and algae to be analogues of the real world.

Probably the best copy of a part of the reef system is found in a deep sand bed that has a thriving and diverse population of animals living in it. Provided the bed was set up with care toward adding the proper organisms, such deep sand beds contain many different types of bacteria, as well protozoans, and a diverse array of animals. In fact, the quantitative sampling that I have done in my own aquaria, indicates that numbers and types of organisms found in the sediments fall within the ranges found in natural environments. Phrased another way, a deep sand bed with a thriving array of animals is really indistinguishable from what would be found in the shallow sand communities of sheltered parts of coral reefs. This is important, as it allows the use of data from investigations of these shallow sand communities to explain what is happening in our tanks. Not all animals in a sand bed feed in the same manner, nor do they all feed upon the same things.

- There are predators that feed on other animals in the sand bed.

- There are herbivores that feed upon either true plants or algae.

- There will be scavengers feeding on dead animal matter.

- There will be detritivores, feeding upon organic debris of various sorts.

- There will be suspension-feeding animals that feed on material floating in the water above the sand bed.

And there will be animals that actively ingest the mineral sediments themselves, and digest off organic material, such as bacteria or other animals that adhere to them.

This wide diversity of feeding types is matched by a wide taxonomic diversity as well. There will be protozoans, which although they may differ from animals in many ways, may be considered to be animal analogues. There will be flatworms, round worms, and segmented worms of many different types. Small crustaceans, also of several different types, are often very abundant.. Numerous snails and echinoderms may also be found, although their diversity is often limited in aquaria.

Most aquarists consider that the major function of the sand bed is to provide some sort of biological filtration. A well-established sand bed does this very well by providing multiple biological pathways for energy utilization. Or, put another way, a multitude of potential food webs for the processing of excess food. Animal physiology being what it is, we always have to feed more food that can be utilized by the animals in our aquaria. Some of this food makes it directly to the bottom as uneaten food, but the majority of added food probably gets eaten by some aquarium organism. Eaten food is always processed rather inefficiently, and a sizeable component exits the animals as fecal material. Fecal material is not waste material, but rather indigestible food, often with a sizeable component of digestive enzymes still active in it. As such it liberates a lot of dissolved nutrients. Dissolved nutrients are really the food for bacteria, and the fecal material is rapidly colonized by bacteria. Both the fecal material and the bacteria on it may be food for other organisms, primarily sediment-dwelling animals.

All of this excess food, processed food, and detritus drifts through the water of an aquarium for an indeterminate time and may, in fact, go to feed coral and other suspension-feeders directly, but most of it reaches the bottom and enters the realm of the deep sand bed organisms. Here it is may be mobilized up in to the water column for one more times before all the nutrient value is lost.

As aquarists, it is to our advantage, and to the advantage of our corals, if we can turn this material into coral food or into food for all suspension-feeding animals. Fortunately, it is rather easy to do this, all it takes is some planning and minimal oversight on the part of the aquarist. The aquarist needs to manage their sand bed a bit, and the sand bed organisms generate a large amount of coral food from what appears to be useless waste.

Things Not To Do.

The aquarist may do two things to either partially or completely remove these food sources. First, they may underfeed their aquaria. Either intentionally or accidentally, aquarists may "turn off" these sources of food by not providing sufficient nutrition to the aquarium. Many aquarists are under the mistaken opinion that coral reefs have little in the way of planktonic food for their inhabitants. This is a patently false idea, but seems common enough in the aquarium hobby. In reality, the reefs are bathed in a continual source of very small and very nutritious food. This notwithstanding, aquarists often feed their animals less than is necessary.

Often underfeeding is done to restrict the dissolved nutrient content in aquarium water. This is an admirable goal, but it should be accomplished by other means, such as nutrient export. On a coral reef, food is NEVER in short supply to suspension-feeding animals. When those animals are put into a standard anorexic aquarium they are severely stressed and become disease prone. The animals need a continual supply of nutritious food.

Only in this way will the animals be healthy and vigorous. A healthy well-fed aquarium will result in a production of a significant amount of internally generated food

The second thing an aquarist may do that may completely negate the production of food from the sediment is to mechanically filter the aquarium. By putting in particle barriers such as screens, filter floss, and filter cartridges, the water is cleansed of all of those nasty food particles, and the aquarist is left with crystal clear, and sparkling water. This is a totally unnatural situation, and will result in the unnecessary deaths of many animals.

Foam fractionation, or protein-skimming, generally removes some of the particulate organic material and it may remove some of the phytoplankton. It will generally not remove many of the larvae or demersal plankton as they have means of avoiding capture or entrapment in the skimmer’s bubbles.

With some foresight, and a little work a sand bed may be constructed and maintained that provides a significant amount of food for suspension-feeders in a marine aquarium. The key to such food production is the proper construction and maintenance of a deep sand bed, followed by the appropriate feeding of the tank with a variety of foods, but including specifically phytoplankton, and small particulate material. Such a system will provide sufficient food to provide much of the food necessary for the proper and balanced nutrition of coral reef animals.

not from me of course but very logical to say the least.

[puttputt]

Mmmm....Its still trying to shake off the zeovit!!!

and fay, I believe you!!

[wasp]

Ever get over the Shore Puttputt?

If so we could arrange a meet, check Crackers too!

I don't get over to Waimauku though.

[puttputt]

yep quite often, (sneak over to see jetski ), would really like that Wasp.

Waimauku isn't that far!!!!

[chimera]

Waimauku isn't that far!!!!

only if you live in waimauku

interesting post cookie, may explain why cracker has got some good growth and colour - has strong lighting for photosynthesis, doses amino acids for protein for zoox, ca for coral skeleton then the usual kh and mg for stability (amonst other things) oh, and a fine sand bed producing, in theory, microplankton as yet another food source

[puttputt]

good article CE.

I guess it's a good time to come clean 8) and admit that I have a 1m refugium with a good thick sand bed in it full of all sorts of life, and like you Cracker the glass in the refugium is covered of copepods of all sizes, amphipods, worms, mysid shrimp, larval stage "plankton" etc. I'm sure the majority of these get through my pumps into the tank.

[chimera]

i always seem to have very few pods, in both my display and fuge. the only animals in the fuge is a brittlestar and a lawnmower blenny, neither of which i'd imagine feed on pods. can you get "pod starter kits" here like you can in the US? or do i just have to ask puttputt politely for a sample of his delicatessens? :lol:

[cracker]

Well there you go then Puttputt.....sand....

Heres a couple of horrible sandbed shots.....

[cracker]

I do believe I got a boost of pods through SKUZZA. I purchased about 30 kilos off him for my tank and I think it was VERY mature. I might be wrong....Skuz?

[cracker]

I also have a small deep sandbed in my sump which I NEVER touch. I can often see pods swimming around this part of my sump.

[wasp]

good article CE.

I guess it's a good time to come clean 8)

HA!! I'm leaning more & more to the belief I do not have enough natural food in the tank.

Anyhow Puttputt I enjoy your posts, when you're over this way next drop me a pm, or call 479-5446 & book in, we'll do Craigs as well.

Cheers Alastair

[0pius]

I now have millions of pods, they live in the macro and micro algae in the tank (Yes macro in the tank, I didn't know what the plant was and when I found out it had already gone sexual and my display is also my fuge) I think I got them when I purchased the live rock of Reef.

[chimera]

well, anyone willing to give/trade some let me know. want to dump some in my fuge and hopefully let them reproduce. the more life the better i reckon

[lduncan]

Cookie, that article reeks of Dr Ron Shimek.

While there are occasional glimpses of reality and truth in it, there are also many other question which have to be asked about the relevance of the article.

Layton

[puttputt]

opius, I have macro in my main tank as well, escaped from the fuge, and regardless on how well I try to control nutrients, its grows well, and drives me crazy.

When I break this tank down, every last bit on every rock will be removed.

On the plus side, the bits of halimedia(sp?) are very nice.

[0pius]

Halimeda is great I love the lok of it and the way it grows although it uses alot of calcium, I have only just noticed this when I examined the amount of corraline growing.

The caulerpa is a different matter, that I could do without.

On the other hand I have nearly no nitrates as a result of these obviously very helpful plants. and my puffers certainly like it

[wasp]

That was a great article Cookie, very helpful.

I suspect Layton may be right it does sound like Doctor Shimek, the marine biologist.

Layton you said you were able to find "occasional glimpses of reality and truth in it". Ha Ha! A good understatement! :lol: Now why do I get the feeling you are going to try to question / argue the contents of the article?

I am actually giving thought to find some way to incorporate sand into my system. Might do a refugium with sand, aimed at meeting the needs of pods, and hopefully some other stuff also.

[lduncan]

I suspect Layton may be right it does sound like Doctor Shimek, the marine biologist.

Nope, Ron Shimek the invert zoologist. He's not a marine biologist.

Layton you said you were able to find "occasional glimpses of reality and truth in it". Ha Ha! A good understatement! :lol: Now why do I get the feeling you are going to try to question / argue the contents of the article?

Well more the conclusions. I could try using Ron's own writings to bring up some interesting questions one the relevance of that article to our tanks.

I'll look through Ron's writings and post something tonight. But here's a question to think about. Isn't the sand bed actually competing with corals for food?

Layton

Layton

[wasp]

I knew it!! You are going to question / argue everything.

Don't tell me, among all your other talents, you also know more than Doctor Shimek the invert zoologist, right? :lol:

[reef]

Nice article Cookie, Looks like the REEF/GERMAN method .

Amino acids, biodigest/bacterial filtration., feeding coral, shallow sand bed,

[lduncan]

Wasp: Nope, conclusions and interpretations I'm looking at. I'll also use Ron's own words to show why some of his conclusions seem strange. Plus some interesting stuff from Eric.

I'll try and spend a bit of time putting it all coherently in one post tonight.

You never know, it might make sense.

Layton

[puttputt]

Chimera, not willing to disturb the sand bed at all, but bring around a natural sponge, drop it in the ref for a couple of weeks and then take it home - should work a treat.

[cookie extreme]

also another very similar article in Marine World by A.J. Nielsen about the same subject. now he used to believe that SPS will live on light alone as so many of us did (and some still do) but he has altered his view quite a bit and now supports the believe that SPS need extra food.

[lduncan]

now he used to believe that SPS will live on light alone as so many of us did (and some still do)

Hold up. Who's saying they will live on light alone?

Layton