Coral Feeding

[lduncan]

Maybe because we have all tried to do this already, and you seem to be either ignoring, not reading or just not getting it. I have given up posting because it was just becoming pointless saying the same thing over and over.

I've read it all, nothing even comes close to suggesting that sandbeds are somehow more beneficial to corals, than not having sand.

Like I said before. Spell it out for me. Go back and re read the very first post. Then provide me with something similar which shows how sand beds are more beneficial, than having no sand.

Cause at the moment, I just don't see it.

Layton

[Caryl]

My point? It just seems to be going around and around

[wasp]

My point? It just seems to be going around and around

I'll agree. There has been quite a bit said about sand beds, even some good articles. Layton says he "can't see it". Blinded by prejudice perhaps?

I'll agree with Joe Blogg it is interesting, but only for people prepared to learn. I think it has reached the circuitous stage now some things are being repeated over and over.

[lduncan]

That's a cop out wasp.

Break it down for me in a single post, right from the start the way you see it. How can having sand in a tank be more beneficial corals than not having sand?

Simple request. You say you've already done it in this thread more or less. Put it all in a single logical post for me.

Layton

[wasp]

That's a cop out wasp.

Layton

Rubbish.

It is not my job that I have to teach the unwilling. if you cannot see what has already been written it can only be 1. prejudice, and 2. argumentativeness.

Having been in more than a few of your arguments before, i know how they always become pointless, as this one has.

Might be what turns you on, but not really for me.

[lduncan]

Rubbish.

It is not my job that I have to teach the unwilling. if you cannot see what has already been written it can only be 1. prejudice, and 2. argumentativeness.

Having been in more than a few of your arguments before, i know how they always become pointless, as this one has.

Might be what turns you on, but not really for me.

Please persist wasp, you don't answer many of my questions. So lay out you thinking in a single post from start to finish. I'm giving you a chance to teach me something here.

Layton

[cracker]

How about we boil this whole thing down to what matters.

If you want to feed your corals more. Physically put more food in your tank.

Don't pretend that by adding sand you are somehow providing more food for your corals or enhancing the nutritional value of it. You're not. If anything it makes it less available.

If you're going to have sand in you're tank, AND feel the need to justify why, at least come up with reasons which are true. Some examples might be as, "i find critters interesting" or "i like the look of sand" or something like that. That's all.

Sand isn't a solution or aid in feeding corals.

Layton

Im sorry Layton, but the above statement really is garbage.

Sand DOES assist to feed coral polyps. It does so by providing:

1: Not quite decayed detritus and food scraps exiting the sand and feeding

2: releasing microscopic critters and bacteria for the coral

3: Releasing nutrients to the water column which can be beneficial to some orghanisms and not so good to others.

Even nutrients released from the sand will feed coral to some extent.

A microscpe would show that there are lots of food types in a sand bed.

[cracker]

What do small almost microscopic pods feed on?

Detritus and undecayed food sources.

Same stuff polyps would be more than likely interested in.

[cracker]

From wetweb...

caption: "Regardless of where you install your deep sand bed (in the display versus a refugium), you can enjoy the benefits of significant natural nitrate reduction (NNR) and plankton production."

Another significant advantage to deep sand beds is the provision of a dense and natural habitat for numerous micro and macro-organisms. Many fishes and invertebrates cannot be kept successfully or at least optimally without a DSB. Some popular wrasses, jawfishes and gobies… horseshoe crabs, sea cucumbers, stingrays and many other featured creatures will not thrive without thick sandy substrates. Countless invertebrates including some corals will only survive on a sandy seafloor (hard substrates like rock are inhospitable to their feeding strategies and polyp cycles). At various and increasing depths, DSBs provide natural foods for these fishes and reef invertebrates like microcrustaceans (amphipods, copepods, mysid shrimp, etc), bacteria and other nanoplankton. DSBs also provide habitat for desirable plants, algae and animals. Seagrasses like Thalassia and Syringodium (Turtle grass and Manatee grass) for keeping seahorses, pipefish or Cassiopeia (Upside down) jellyfish, for example, require very deep beds at 6†minimum.

The limitations and potential pitfalls of employing a DSB’s are far less mysterious or unpredictable than previously thought. In fact, deep sand bed methodologies now have a history of more than 20 years in use and may fairly claim to be regarded as “tried and trueâ€. Your first decision to make on contemplation of the strategy is purpose. Although you will likely enjoy a combination of benefits with any interpretation of the strategy, some methods are more effective than others in various aspects. Choose from the above described potential benefits and focus on which ones suit you best: aesthetics, nitrate control, or plankton production to begin with. If your purpose for using sand (in contrast to course gravel, shell forms or nothing at all) is only aesthetic, you may wish to forego very deep beds altogether and enjoy a shallow substrate (less then 1â€/25 mm) with little regard for sand grain size; there are few benefits or risks in doing so. Nitrate control, instead, is best achieved with sugar fine sand. Zooplankton production (amphipods) to feed fishes may require more coarse sand. And coral propagation (active “fragging†by the aquarist) will often demand a dressing of rubble atop any substrate for a faster settlement of clones and divisions.

After an introduction to the merits of deep sand beds and the “living substrates†you might ask yourself, “what really is live sand?†Live sand is essentially a combination of non-living substrate (usually calcareous in composition but it can be silica-based) with a myriad of tiny beneficial life forms infused throughout it. There are beneficial organisms living on (meiofauna) and between (infauna) the substrate. Creatures found in this medium range from visible zooplankton down to a wide range of microbes dominated by bacteria. Indeed, live sand is much more than microbial colonies battling it out for space and nutrients. All phyla of marine life have representation in sand on the living reef. Some of the most commonly encountered organisms are segmented worms (annelids), roundworms (nematodes), micro-crustaceans (amphipods, copepods, mysids and the like), and bivalves (mollusks), but there are many, many more organisms in tow.

By the activities of live sand organisms, a DSB imports many nutrients, export others, and serves as an extremely efficient living "filter" at large. Space and food are exploited by the colonization and proliferation of crucial microorganisms. Other undesirable elements from the water are simply precipitated and bound into the substrate. Live sand certainly is a complicated and fascinating microscopic world of its own, and quite worthy of a closer look... so get that magnifying glass or microscope out! There is a veritable microscopic zoo to browse.

[suphew]

The secondly, and I know nothing about marine bacteria, but I do know that in fresh water there are many times the amount of bacteria living on surfaces that in the water. A sand bed has a huge amount of media and surface area, perhaps this explains why it works? Also my understanding of BB and suspending matter in the water was so that the skimmer is able to remove it? This would explain why in two identical tank, fed the same, one without sandbed, that the corals get more food with the sandbed. Because the sand bed puts it into a form the corals use (bacteria), where as in the BB it is skimmed out.

This was the second post. In BB you keep talking about the food you put into the tank ending up in the water and feeding the corals. But as soon as you put it in, the skimmer starts taking it out, so in a short period of time, all that food you believe is still in the tank growing bacteria and feeding the corals has actually been skimmed out, or at least the level of it is steadily dropping. With a sand bed some of that food ends up being held in that tank, converted in the sand bed either directly into bacteria, or via critter pooh/deaths into bacteria. This is constantly being released back into the water column. This isn't hard to understand???????

[lduncan]

Im sorry Layton, but the above statement really is garbage.

Sand DOES assist to feed coral polyps. It does so by providing:

1: Not quite decayed detritus and food scraps exiting the sand and feeRing

2: releasing microscopic critters and bacteria for the coral

3: Releasing nutrients to the water column which can be beneficial to some orghanisms and not so good to others.

Even nutrients released from the sand will feed coral to some extent.

A microscpe would show that there are lots of food types in a sand bed.

It's not garbage at all. It's fundamental. If you don't agree with that, then you're not looking at things logically.

1. Do you need sand to decay the detritus? No. Were does this detritus come from initially. The food YOU put into the tank. The sand bed isn't putting any additional food into the tank.

2. Do corals require critters to live? No. Are critters the most nutritious form of food, considering they eat more nutritious coral food? No. Do you need sand for bacteria to decay detritus? No. Doesn't a lot of this food just accumulate in the sand bed, with only a portion even getting anywhere near a coral polyp? Yes.

3. Do you need sand release the nutrients from the food you feed? No.

Still don't see anything which supports the theory that adding sand is more beneficial to corals than no sand.

Layton

[cracker]

And this says it ALL.

If this doesnt open minds and TEACH something, Nothing will.

FROM REEF-AQUARIUM...

The Importance of a Deep Sand Bed

The most important component of a coral reef aquarium is a deep sand bed, comprised of very fine sandy sediments.

Benefits

Most coral reefs are surrounded by sand area and by constructing a sand bed in our aquariums we merely emulate nature. These beds provide three things. First, they provide a place for processing and exporting some dissolved nutrients. Second, they provide a place to recycle detritus, excess foods, animal feces and other particulate material into useable forms. Finally, they provide a food source for many reef animals. Let's look at each of these functions.

As they do in nature, the sand grain surfaces of sand beds in our systems provide the major substrate for nutrient processing bacteria. The bacterial population is determined by three factors: the total sand surface area; the amount of nutrient available; and the number and effects of bacterial predators. All of these play a role in the development of the sand bed biological filter.

In a given volume of sand, the usable bacterial surface area rises rapidly as the average particle size decreases. The total sediment surface area in even a small tank is impressive, indeed. In a 45 gallon reef tank where the sand bed averages about 4 inches deep, by 12 inches wide, by 36 inches long, for a total of one cubic ft of sediment. If the average particle size is one eighth mm, and that is a good average size to have, the total sand surface area is about 14,828 square feet or just slightly over 1/3 of an acre. A LOT of bacteria can live with that amount of space! The surface area for bacteria and microalgae in live rock or on other surfaces is insignificant compared to the area in a sand bed four or more inches in depth.

Although we seldom consider bacteria when we set up our systems, they are exceptionally important to the survival of every decorative fish or coral we add to the tank. Those bacteria are the biological filter of your reef tank, and by their simple existence and growth they detoxify and remove many of the excess nutrients from the system.

One organism's poison is another's nutrient. Fish and invertebrate urine, largely ammonium hydroxide, or ammonia gas dissolved in water, is the primary byproduct of necessary protein metabolism. Ammonia gas, even very small amounts dissolved in water, is highly toxic to animals. Likewise, phosphates are also byproducts of animal metabolism, and although not toxic to most animals, high phosphate concentrations reduce or stop coral growth. The removal of both nitrogenous wastes, such as ammonia, and phosphates is accomplished by bacteria and microalgae which absorb these toxic animal byproducts and use them in their growth as necessary, required, and vital nutrients.

The cardinal rule of animal husbandry is that you have to feed animals, and many reef animals need to eat a lot. Simply feeding your fish or corals the necessary food they need to live may boost ammonia and phosphate concentrations several hundred to several thousand times what is normally found in reef water. But, if you have a deep sand bed, a process that is nothing short of miraculous occurs. The bacteria and algae living in the sediments take up the nutrients so fast and so thoroughly, that hobbyist test kits typically may not measure any of the nutrients at all even immediately after feeding.

These nutrients act as food for the bacteria. In a very real sense, the biological filter depends upon bacterial growth. The breakdown of nitrogen compounds to nitrogen gas is done by bacteria growing in the areas of lowered oxygen concentration in the deeper parts of the sediments. At normal reef temperatures, around 82 deg F, some bacterial species will double their population in less than a half hour if they have the appropriate nutrients. This rapid bacterial growth rate causes the release of nitrogen gas which becomes visible as bubbles in the sediments.

Rapid bacterial growth rates only occur without competition for space or nutrients. As the bacterial populations fill in all the open spaces growth slows and may stop altogether. Some bacteria also secrete a exterior covering called a glycocalyx. These are made of a hard sugar-like material similar in consistency to rock candy. Rapid bacterial growth may produce so enough of this material to glue sediments together. These sediment lumps may be glued so tightly together that hammering is needed to break them apart.

Lump formation is a disaster for the biological filter. The lumps restrict water flow and trap organic material where it can rot. Additionally, lump formation shuts down the biological filter by covering the bacteria and preventing them from metabolizing nutrients. This, in turn, causes the tank nutrient levels to skyrocket.

Fortunately, prevention of sediment clumping and the simultaneous maintenance of optimal biological filter operation is easily done by the establishment of a healthy and diverse sediment dwelling fauna, or "infauna." The infauna, so-called as the FAUNA lives IN the sediments, is a very diverse array group of wonder-working organisms. Unfortunately, they are small, and are not particularly attractive. But they do most of the work in keeping any reef tank functional.

The infauna are "the clean-up crew" and the "reef-janitorial" staff, and the array found in a successful tank may be DIVERSE! More than 200 different species commonly are found living in a mature sand bed. These include many types of flatworms, round worms, dozens of species of bristle worms, small snails, brittle stars, small sea cucumbers, protozoans, and many types of small crustaceans. The total populations may be immense.

What does this diverse and abundant array of critters do for and in the sand bed? Well, some will eat excess food, detritus, or algae. In doing so, they utilize it, and excrete part of it as waste. In turn, bacteria utilize that, and thus the infauna help keep the biological filter going. Additionally, many infaunal animals burrow ingesting some sediments as they go. They digest the microorganisms off of them, opening space for bacteria to grow.

By moving through sediments, the animals jostle and move the particles. Not much, just a little tiny bit. It has been estimated that each day each small organism moves about 10 to 100 cubic millimeter of sediment. Multiplying this tiny average amount of jostling by the number of animals in the tank gives the total amount of disturbance. With this amount of jostling and sediment eating, sediment clumping the sediments will simply not occur.

Consequently, excess food is eaten and disposed of or recycled as animal or algal flesh, and that the biological filter is maintained in the best of condition. And, best of all you, as the aquarist, didn't have to do anything. The animals did it all for you. All you had to do was to sit back, and enjoy a healthy tank. And, yes, I know it was a dirty job, but somebody had to do it....

But this isn't all the good a sand bed will do for your system! Most of the infauna live a year or less. However, they grow rapidly and start reproducing within a few weeks after they were spawned. Cumulatively, they produce large amounts of small eggs, sperm, and larvae that are liberated invisibly into the tank's water. All the spawned material has the potential of becoming food for many small-polyped stony corals as well other filter feeders. It is no coincidence that, historically, aquarists began to be able to keep many of these small polyped corals when they started keeping a sand bed in the aquarium for the first time.

What's all the fuss about sediment grain size, anyway? The answer simply is that sediment particle sizes determine the acceptability of the sediment to the organisms. Most sediment-dwelling organisms appear to have precise preferences. However, most will also live at least marginally well in mixed-sediments with sizes around their optima, and most sediment particle size optima seem to be in the range of 0.050 to 0.200. Consequently I suggest a range averaging about 0.125 as a good compromise. It isn't specifically the best for most infaunal species, but it will allow a diversity of species to live pretty well.

Coarser sediments such as gravel or crushed coral are simply too big. Additionally, they have the drawback of being sharp edges that are abrasive to many of the small crustaceans and worms that must crawl through the sediments. Finer sediments can pack so tightly together that they are impervious to most animal movement, creating a layer that restricts animal and water flow shutting down the biological filter.

Having to assess sands for particle sizes would be a daunting task for any hobbyist. Fortunately, however, several vendors sell bulk sands in the appropriate size ranges, often marketed as "sugar fine" or oolitic sands. A few larger particles in the sediment mix is okay, but larger sediments should not constitute more than about 15 percent of the total. Under NO circumstances should you use crushed coral or coral gravel. These substrates are too coarse and often too abrasive for many of the smaller organisms to survive in.

Additionally, there are several vendors offering "detritivore" or "recharge" kits having several different types of animals in them. Kits from different vendors are complementary rather than competitive. Adding one kit is good, adding two is really better. You will get a more diverse system faster with more kits. However, their cost may be prohibitive. Once the kits are in, let the system go for at least two weeks without adding fish to allow the live sand animals to establish minimal populations. Remember these are living animals, and will need to be fed.

Within a week, you should notice bubbles in the sediment next to the glass indicating the sand filter is working, within a couple weeks small tube traces should be visible in places in the sediments near the walls, and small bug populations should be evident. UNDER NO CIRCUMSTANCES SHOULD YOU ADD "SAND-SIFTING" ANIMALS SUCH AS BURROWING SEA STARS OR SOME GOBIES. These animals are "sifting" the sediment to eat the sand critters that you need to have thrive.

Problems

More imagined than real problems bedevil keepers of sand beds. The imagined problems are proposed by people who are ignorant of the sand bed dynamics. Among these imaginary problems are accumulations of hydrogen sulfide and detritus, and the need for sifting. Hydrogen sulfide will indeed be formed in the lowermost layers of a deep sand bed. It will NOT migrate up through the sediments to poison a tank. Hydrogen sulfide is an amazingly toxic gas, but that toxicity is exceeded by its pungent rotten-egg odor. The gas will have an exceptionally strong odor, and will seem overwhelming at levels well BELOW toxic amounts. If you can smell this stuff without it literally taking your breath away, it won't be at a harmful concentration. There is no real evidence to indicate that it may reach toxic levels in a deep sand bed.

Detritus build up in the sediment is another non-problem. If the sediment fauna is thriving, there will be a slight build up of fine detritus while the rest will be processed by the infauna. The final imaginary problem, the presumed need for sifting in a healthy sand bed, simply does not exist. Small organism movements "sift" the sand sufficiently. Any other sifting of a healthy bed will cause serious harm.

Sand beds recycle materials and export many of the excess nutrients in an aquarium. Some excess nutrients are mobilized by becoming soluble through metabolic processes and need to be exported either as harvestable macroalgae or animals, grown in the main tank or a sump.

The only real problem with a sand bed is the reduction in diversity as the bed ages. This is caused by extinction and replacement problems because the volume of our beds is simply too small for some species to generate self-sustaining populations. This is remedied, by purchasing a detritivore or recharge kit or two every year or so to give a boost to the fauna.

Conclusion

The installation of a live sand bed is easy, straight-forward, and inexpensive relative to almost all other aquarium purchases. Once established, such a bed will contribute much to the success of a reef tank by providing a biological filter with sufficient capacity to for most tanks. Additionally it will provide food for many of the suspension feeding animals such as small polyped stony corals. And, it will do this all with a minimum of care and expense.

[cracker]

It's not garbage at all. It's fundamental. If you don't agree with that, then you're not looking at things logically.

1. Do you need sand to decay the detritus? No. Were does this detritus come from initially. The food YOU put into the tank. The sand bed isn't putting any additional food into the tank.

Sand critters will break down the detitus and food to microscopic sizes

2. Do corals require critters to live? No. Are critters the most nutritious form of food, considering they eat more nutritious coral food? No. Do you need sand for bacteria to decay detritus? No. Doesn't a lot of this food just accumulate in the sand bed, with only a portion even getting anywhere near a coral polyp? Yes.

Small critters and ourselves move and disturb the sand releasing food sources into the water column.

3. Do you need sand release the nutrients from the food you feed? No.

not sure what you mean there

Still don't see anything which supports the theory that adding sand is more beneficial to corals than no sand.

Have you read my last post.....and dont say its not proven science either please.

[Feelers]

I think it's great that Layton carries on the debate, just because he is in the minortiy I dont think less of his opinion or that he should stop. He is very well versed in the literature, and this gets everyone else reading too.

I enjoy a good argument, and so do other regular posters.

Afterall he started this thread - noone else had to reply, it was very clearly setup for a debate.

Layton I think the science is still missing for the nutritional value of bacteria vrs eukaryotes - I also think a DSB makes a very alien environment from the natural reef, so everything is very much speculation on both parts.

What happened with your DSB?

[misnoma]

I'm stunned this has made it to page 8 without anyone throwing their toys too far :lol:

It's been a great read too

[cracker]

Layton, you havent replied......

[cracker]

[lduncan]

I don't live here cracker Got more productive things to do.

I think it's great that Layton carries on the debate, just because he is in the minortiy I dont think less of his opinion or that he should stop. He is very well versed in the literature, and this gets everyone else reading too.

I enjoy a good argument, and so do other regular posters.

Afterall he started this thread - noone else had to reply, it was very clearly setup for a debate.

Absolutely, it's the whole point. A bit of debate, to get people thinking, and reading, hopefully from a variety of different sources.

Layton I think the science is still missing for the nutritional value of bacteria vrs eukaryotes

Even the DSB advocates agree with that. It's just plain fact. Common knowledge. Chitin is not digestible by most animals, including coral polyps. If you want to do some searching on corals in particular, you should have access to all the papers you want through the university library website. Search for work by Sorokin, he's done a fair bit on coral feeding, metabolic rates and related stuff from the late 70's through to early 90's. I only have access to abstracts, now I'm no longer enrolled.

- I also think a DSB makes a very alien environment from the natural reef, so everything is very much speculation on both parts.

Well apart from the whole subduction and plate tectonics aspects they are surprisingly similar in tanks as they are in nature. It's just that some people think that when you put them in tanks, only the desirable aspects come, and the undesirable ones magically don't happen. Or that you can stop all those undesirable things happening by using critters. A lot of hobby writing doesn't explain how they really work in nature.

What happened with your DSB?

It was a couple of inches of fine river sand in a remote type setup it was using it to reduce nitrates to zero (They had been around 5 for several months after I moved the tank). It served it's purpose as far as the nitrates went. But it's started to turn bad, I had a couple of rocks embedded in the sand, and could tell that as soon as they started to grow a little hair algae, the bed had gone from a storage cycle to a release cycle. So I just dumped it.

Then I found that UV is actually a far more effective solution to reducing nitrate and boosting useful bacterial populations. Without the side-effects of other methods.

Layton

[cookie extreme]

Then I found that UV is actually a far more effective solution to reducing nitrate and boosting useful bacterial populations. Without the side-effects of other methods.

if you nuke them with UV and without live sand how do you hope to reproduce them in your water coloumn (that is once they survived the skimmer of course) into sufficient numbers?

[lduncan]

Bacteria don't rely on sand for anything. They may go on to lead perfectly normal lives without it.

But basically bacteria are very efficient. You don't need anywhere near as much as you think to get the job done. Anymore is just more bioload. They coat every surface in the tank, every crevice in every rock. There is no shortage of places for them to live. The fact that you nuke a few in the water is completely insignificant, they could just as easily get skimmed anyway.

There was a study done which showed that while using UV reduces populations of water borne bacteria, it can actually boost the total population by increasing other types by providing more efficient food sources which result from the chemical bonds the UV breaks in larger organic molecules.

From memory they were actually looking at some of the same bacteria (P. denitrificans) which perform de-nitrification in our tanks. Pretty interesting.

Layton

[suphew]

There was a study done which showed that while using UV reduces populations of water borne bacteria, it can actually boost the total population by increasing other types by providing more efficient food sources which result from the chemical bonds the UV breaks in larger organic molecules.

Doesn't using UV contradict your whole bacteria in the water column feeding the corals theory??

[lduncan]

nope.

[suphew]

nope.

Can you explain please? Cause I dont get it.

[lduncan]

What don't you get? The UV doesn't remove anything from the water, just changes it.

[suphew]

There was a study done which showed that while using UV reduces populations of water borne bacteria

You suggest not using sand because it takes nutirants away from the water column lowering the amount of food for bacteria and therefore corals, yet use UV which kills those same bacteria anyway? Seems weird to me.