Ron

For many years the conventional wisdom was that overfeeding led to high nutrient levels in the water and algae blooms, both of which were bad for corals. I am finding it hard to reconcile the idea of heavy feeding with the goal of low nutrient levels.

The problem with the conventional wisdom is that it basically treats corals as plants, and unfortunately they are animals. Indeed amongst predators, they have the largest percentage of their bodies devoted to food capture of all predators. You would think this would tell folks something...

While the dissolved nutrients in the water over a coral reef are indeed low, particulate nutrients are not, and most corals, particularly the so-called SPS corals (SPS is a term that really has no biological meaning), are adapted to catch small microplankton. There is a lot of this stuff hitting a reef - estimates range from about 100,000 particles to about 1,600,000 particles with a total weight of between 2 - 15 ounces of wet weight per square meter per day. Most of this blows by any given coral in the breeze but the entire reef top pretty well cleans it out of the water.

Bottom line corals are adapted to feed, and need food for complete nutrition.

Our problem is to balance food input and export to keep the level of dissolved nutrient low. A good sand bed fauna and a good skimmer will generally keep the nutrient levels low. Growing some macro-algae growing in some part of your system will allow you to export even more excess.

It just doesn't make any sense to me that people fought for years to get nutrient levels low (presumably because high levels brought bad results) and now people feed heavily instead. Can anyone shed any light on this?

The people who for years fought to get nutrient levels low were basically aquarists with no real idea of the requirements of the animals.

Keep in mind the concept that has been taught by these folks that "corals are delicate."

WRONG. These are animals that can live for thousands of years in one of the physically most demanding of evironments (coral reefs have benign temperatures - but consider standing on a coral reef crest during a hurricane or even during strong tidal surge). Corals are rugged animals that can withstand damn near anything you can throw at them if you keep them in conditions around their physiological optima and feeding them well. Under these conditions, light to moderate dissolved nutrients are not a problem.

Eric

Just so people don't get confused, may I underscore the differences in the term "Nutrients" and the various ways corals and other animals get these substances

1. Nutrients that are the products of photosynthesis. The common symbiotic relationships found with animals and photosynthetic algae and bacteria are an adaptation to this "low nutrient" water. This is typically high carbon content stuff, and a source of metabolic quick energy and much is lost in the production of mucus (which then feeds other things).
2. Dissolved nutrients; these are things that we measure like NO3-N, NH4, PO4, etc. On the reef, most N is ammonia as nitrate is so low. The levels are very very low. Not so in most tanks, even when measurably low by test kits. If reef waters were higher in dissolved nutrients (excluding some turbid areas), then you would have proliferation of phytoplankton and algae. Corals are successful where dissolved nutrients are low because they both feed heavily on 3 (below) and have the advantage of the phostynthetic symbionts. When nurient levels get high, coral reefs start to lose diversity, eventually disappearing. However, where dissolved nutrients are higher, prey is also high though light is low. In such cases, corals still exist, but they don't form reefs and they are mostly if not totally asymbiotic.
3. Nutrients derived from prey capture; this is what we are lacking and where corals get such a large percentage of their nutrition. Capturing food. Particulate matter (detritus, mucus, etc.) is dead and a valuable food source. It is less desirable than living plankton other prey organisms because it gets acted on quickly by decomposition which tends to increase dissolved nutrients. However, if the dead particulate matter is not too much (like when sedimentation from storms,e tc. occurs) and remains in the water column, the many mouths will eagerly consume and convert to biomass before degradation occurs. It is also typically high carbon content, but is enriched by bacterial biomass that grows on its surface Live prey is considered "nutrients" in that its consituent matter is part of total organic stores, but does not degrade water quality.

There is also the concern of long-term saturation of rocks and sand with excess nutrients which eventually start leaching back into the tank water and cause endless blooms.

I am quite convinced that this is an old wive's tale from within the hobby populace. While it may be possible to thoroughly inundate sediments, it is my experience this would take a massive long term overfeeding with heavy sinking foods. The biofilms, microbial flora and pore structure of rock would not allow for "saturation and leaching of hard substrate. Algae would grow and trap further POM and absorb DOM long before you would "saturate" live rock. The turnovoer time of interstitial water in calcareous substrate is incredibly long.

know a local reefer whose three-year-old tanks, never a problem before, are now starting to develop massive and endless hair algae plagues. He is convinced the rocks and sand are saturated with nutrients and that he must break down the tank and start over with fresh rock and substrate.

There are islands where volcanic activity has caused compostional changes in some "live rock" to include high amounts of various organic and inorganic material. The Cook Islands, for example, are reported to have reef structures enriched with phosphate, and metals are incorporated into other areas. However, this is comparatively rare and I would suggest your friend probably has other things happening besides what he is convinced himself has happened.

I am curious what the heavy feeders are using for substrate. Gentlemen? I know Dr. Shimek uses oolitic sand, but is that true of all the heavy feeding tanks?

Oolitic is kind of a misnomer, as it is a description of the shape - it means egg-shaped rock. I use beds 4-8" deep, in some places only 2", of mixed grain sediments, predominantly fine grained (although even the fine grade aragonites like "Aragomax" are not all that fine by sedimetary standards and are classed, I believe, as a medium to medium fine sand). I want the spatial heterogeneity for biodiversity and the fine grain sizes for productivity. I have had sand beds (originally from "live sand") since 1993 and can no longer qualify what exists in any one system over so many years, additions, subtractions, moves, etc. Its a deep old sand bed with silts, muds, sands, rubbles, and rock.

Ron

Phosphate that is "significantly turned over" is a long ways from saying phosphate is completely recycled. You can still have a net buildup, no?

Yes. It is in the organisms. That is why I suggest to each and all that there has to be export. With export there is no appreaciable build up in organic phosphates beyond the standard organism load.

Also, by an increase in total PO4, can't it be assumed that some percentage of this will in fact be inorganic phosphate, which is why the potential concern was raised in the first place?

Well, I suppose that is the focus of the concern. But there is no evidence that there is any inorganic phosphate in any our systems with a good functioning sediment biota.

Also, are you familiar with the paper by Entsch that was cited in the piece? What did that reference suggest to you?

It suggested to me that in conditions rather significantly different than our systems, that phosphate precipitation could occur. Refresh me, if you have a copy of this paper, on what conditions were necessary for this precipation to occur. If memory serves, and I read this paper some time ago (1988, if my notes are right), I don't believe this is any more likely than the normal precipation of oolitic sands in our tanks. I think you need hot waters, waters with relatively high phosphate concentrations, high pH, and relatively low circulation. Few of these conditions are met in our systems.

To clarify, it's not just vacuuming that is proposed, but rather removal and replacement of 10% of the bed. If you are simply removing this amount of material, how exactly are you causing the demise of surrounding fauna?

The analogy here is dredging a marine sediment bottom. You disturb the burrows of many organisms which can result in their mortality, and you alter the chemical composition of the pore water which can cause a fair bit of mortality. This mortality is localized in a halo around the disturbed area.

And won't the fauna left in place quickly re-populate the new material?

Some would. However, organisms are distributed in patches in nature and in our tanks. Removal would increase the likelihood of totally removing patches or various species from the environment completely. New sand, if non-live (unlive, like the Dracula of sands, instead of undead...) would lack the food necessary to for animal colonization. This process could take awhile. Basically you are resetting the "ecological successionary clock" in those sediments and in removing this you are removing the longer lived organisms.

Also, if you are replacing with live sand, you are providing more "seed" fauna anyway.

Please see a lot of the discussions of what is in live sand these days from this list's archives. From most vendors all you are adding is wet sand, with bacteria and protozoa in it. The essential macrofauna are largely lacking.

Taking it further, if you replace the material with some "enhanced" products like those touted on the list from IPSF or Inland, isn't possible you could be improving your overall sand bed health?

Sure, anything is possible.

If you have a thriving and functional sand bed, why vacuum it out to replace it with some more material from somebody else's bed. It would make more sense just to add this on top of the stuff already there.

And Ron, if memory serves, you saw some merit to this very article when it was first discussed on Fishnet some time ago, did you not? What has changed your mind since?

I am older and wiser....

Actually if memory serves, and we are delving back a long way now... At that time, live sand as thought of by most hobbyists consisted of sand with just a bacterial bed. In such a system, that is one without a normal sediment fauna, there is the possibility of the accumulation of all sorts undesirable nutrients.

However, once the sand is populated by a large animal component as well as with thriving microbial, protistan, and algal (horrors) components, I don't believe such an accumulation is possible, and any desireability of this process.

In part this has been an educational process, where there has been a concerted effort by a few reefkeepers (Eric, Rob Toonen, and myself of this list along with a few others) who also had some background in marine and coral reef ecology, to bring such concepts as normal reef temperatures, feeding of animals, ecosystem approaches to reefkeeping in the hopes of curing the obscene situation of having potentially immortal animals perish after a few months and having the aquarist crowing that they had "kept such and such alive for six (or whatever months)."

Long-term care is the only future for our hobby and it has to be versed in a solid science base, not mythology, and not the unsuccessful practices of the past.

I think you may be giving folks the wrong idea with the word vacuuming. I'd prefer the term siphoning out.

Lets combine the terms. Call it vacuuming the sand by siphoning it out...

So by following this advice, one can take a perfectly healthy system, kill the sediment fauna, and cause the very problem you wanted to prevent.

That's a pretty wide brush you're painting with, don't you think?

Not in the least. This practice is a small scale practice of dredge and replacement habitat remediation. It will work in seriously polluted systems - no question and no argument.

My concern that is that it will be used in perfectly healthy systems. Basically like removing a perfectly healthy heart from a patient and replacing it with a hand pump....

Eric

Phosphate that is "significantly turned over" is a long ways from saying phosphate is completely recycled. You can still have a net buildup, no? Also, by an increase in total PO4, can't it be assumed that some percentage of this will in fact be inorganic phosphate, which is why the> potential concern was raised in the first place?

No, not completely recycled - you're right. But, the phosphate cycle, simply, has a loop from dissolved phosphorous to plants to animals, and then splits b/t phophatizing bacteria or direct animal excretion back to dissolved phosphates which then loop back to plants or become bound in marine sediments, then to rock and are released by erosion. No one has done a study of bioerosion or mechanical erosion in aquaria, but its not likely to be happening on the time scales we are concerned with.

Bob

Bound in marine sediments. I believe that is exactly what Bob is proposing. Another means of export, though you can question the viability of it all you wish. And I agree that no one has or is likely to do the study, but you guys wish to quickly discount the premise? Interesting.

Not happening in reasonable time scales? Are you telling me that you don't see dissolution of your sand over the course of even 6-12 months? This is totally counter to what I experience. If inorganic phosphate is being bound in the sediments(as some of the evidence suggests), then the slow dissolution of our sand beds could most definitely be a problem.

Eric

Actually, i am not at all convinced yet that there is much sand dissolution occurring. It appears to be dissolving, but I think much of it is simply settling. However, I retract that entirely for those using Calcium reactors. Even if does occur, and at an appreciable rate, no one I am aware of has measured a sampling of various potentially bound phosphates from pre-addition sand to removed sand over x amount of time. Finally, the rate of phosphate mineralziation is probably assuredly higher in calcifying organisms. My corals aren't eroding faster than they are growing, nor are my corallines decreasing faster than they are growing...thus we have net uptake of phosphate, right? Who is doing the binding on the sand grains? You would first have to have the sand grain increase in size during phsophate mineralization and then decrease as it is released by erosion! Anyone seeing their sand beds getting taller?

Unless, of coursse, you suggest that simple calcium carbonate is acting as a phosphate sponge. If this is the case, then simply adding sand should suck up the phosphate from our water like a phsophate sponge! Gee, maybe we should tell the manufacturers to stop using aluminum oxide and start using sand! LOL

Here's an experiment. Place a small bowl with, say, six grains of sand in it. When those six measly grains have dissolved without doing anything, let's pick up the discussion again! ;-)

Basically, that leaves us with the plants. Algae, mainly. Like coralline algae, turf alage, zooxanthellae algae, phytoplankton algae, macroalagae, whatever. 300 ppm are found in some sedimetns by Entsch. It is a significant stored of bound phosphate, but you are talking about a heck of a lot of complete erosion to liberate even a fraction of that amount, even if phosphate were being biogeochemically bound at an appreciable rate in aquaria.

Bob

That's 300 ppm by weight, remember. Even at the slow? rates of erosion that we see in our captive systems, if 300 ppm resides there, we gotta big problem, because at the rate my sand bed dissolves I'd be liberating a whole bunch of phosphate. IMO, more than even the most efficient means of export could keep up with. In this case, I don't think the natural study necessarily carries over to the captive for this example.

Eric

Me neither. see above post.

True, but what data supports rates of phosphate being bound in carbonate structure in aquaria? There is a difference between finding organically enriched areas with locally high nutrient levels and problems. When you remoive old sand bed, you remove the organic mateiral contributing to its productivity, too, which includes phosphates among other things. This doesn't mean its a problem. I think people are operating under the assumption that the pore structure of a sand grain is like some bizarre sponge that sucks up phosphate and holds it there until it reaches some dangerous level, or can't hold anymore, and then it starts releasing it again, en masse, to be problematic. In fact, it doesn't happen this way. And so if we are dealing with non-eroded sediments containing a set percentage of bound phosphorous, the replacement sand could have even more depending on its geochemical history.

Bob

I doubt there is any study which quantifies the rate of deposit, but certainly you're not suggesting it doesn't happen at all? The lower levels of our sand beds experience low enough pH levels to promote dissolution, do they not? If you've got PO4 bound into the sediments at the time they reach these lower levels, don't you have a net release occurring?

Doesn't happen this way? Why would it not then? If we assume that we're removing material with PO4 bound up in it and replacing with fresh amounts of the same material, wouldn't it be fairly obvious we have a net reduction? There's several assumptions made there, but you get the point, I hope.

Eric

How are they being bound, and then released? Why is sand supposedly dissolving, but not rock and coral? Because of the low pH? Please help with the pH matter, because I am not remembering the studies that measured pH values in aquaria sandbeds.

I am not convinced there is significant bound phosphate over time in sand grains and I think the majority of phsophate cycling occurs in other ways. However, for argument sake, let's say there is significant dissolution of sand by low pH, various erosion, etc. So, I think we have concluded that sand is not a viable susbtitute for a phsophate sponge and we can't hang a bag of it in our sump, right?

So, we have to have net phosphate accretion at a concentrated level above what normally exists in the pre-addition sand, right? You aren't seeing phosphate problems with your calcium reactors, right? So, then we have to accrete this phsophate by external organisms who dwell only in the sand, right? Sand's not alive, so somethign has to cause it to accrete and "bind". We thus assume that the accretion will occur on exposed surfaces (the outer layer, so to speak.) Then, some form of erosion has to occur to liberate it or cause it to "leach." And, it will also release faster than it is bound to cause an increase in phosphate levels, right? Evetually, then, and to have a net dissolution of sand, you would also have to be eroding the original calcium material which we have assessed as not having high phosphates. Thus the net loss of phosphate would only equal what originally went into the tank and was dissolved at some point before being "bound." If this amount wasn't problematic, we are then assuming one took long term bound phsophates and released them over a very short period of time. Very hard to believe, imagine, and certainly far from being proven. Do you follow the logic here? Make sense? That's my theory, subject to revision in there is some data that i am missing or forgetting. Open for further talks!

That's a pretty wide brush you're painting with, don't you think?

Well, not really. You are correct in the repopulation scenario - simple replacement may not pose long term imbalance, but it disturbs oxic layers, removes wanted species and flora, and in general puts you back to square one for the replaced area and likely disturbs adjacent areas, too.

Bob

I was referring to the gloom and doom theme of Ron's post. How does it put you back to square one, exactly? Especially when it's been suggested that an occasional inoculation of "wonder mud", "detrivore kits", etc. will benefit the bed. Sounds a little like the same effect you get with replacing some sand, doesn't it?

Eric

My understanding is that chemical energy in the ATP bond is released when the bond is broken. ADP and a phosphate are still left over. Matter is not destroyed nor converted into energy; instead, chemical energy is released, partly as useful energy and partly as waste heat. Total mass has not decreased. My understanding is that mass is never converted to energy except in the case of atomic fission/fusion reactions or matter/antimatter annihilations.

I'm sorry... I'm not talking about splitting atoms, I talking about chemical bond energy, etc. When you have a reaction that liberates x amount of joules of energy as heat or whatever, it is most certainly not matter. Its energy. Simple combustion is the release of energy, usually as heat, from matter. See Mark's post. In any event, this certainly does not change the Pyramid of Biomass, which is an Ecological Law not meant to be broken...not even among reefkeeper's. ;-)

If you add phosphates to a tank, there they will remain until removed by harvesting algae, skimming, or some such. As long as phosphates are being taken up by macroalgae and not hair algae it is probably easy to control. I suspect that people who have had bad hair algae outbreaks do not have other macroalgaes such as caulerpa in their tanks, but who knows.

A problem here is that you are are forgetting that your tank, too, is filled with algae. You know all that pretty purple stuff? Now, my tank (and yours, too, hopefully), is showing net growth. In other words, I hope the powerheads are getting more and more corallines on it, and that the corals are growing. To release bound phosphate from bioaccretion, the corallines and corals would have to become eroded and then broken down by microrganims and chemcial bioerosion to its constituents.

Alternately, you are correct. You can export phosphate by algal removal, coral removal, water changes, skimming,etc. However, it is my (humbly) extensive experience that accumulation of phospahtes in my systems without any effort in net export, if it is occurring, appears to be on the order of years to decades. Now, if I am so lazy that if I find my phosphates have risen to .3uM five years from now and I refuse to do a water change, I guess I don't ned to be keeping a reef tank anymore. I can't speak for everyone, and perhaps others might see accumulation much more rapidly... I'll leave it up to them to explain what's happening in their own systems.

Trust me, I'm no magician or miracle reef keeper, and I put really inordinantly little effort into my tanks. Nor am I offering anyone "the plan" or "the way." I'm just telling you what happens, why I suspect it happens, and some science behind my reasoning.

I suspect that people who have had bad hair algae outbreaks do not have other macroalgaes such as caulerpa in their tanks, but who knows. I will ask my friend with the sudden (after three years) hair algae problems if he has caulerpa in the system. Maybe adding caulerpa would end his problem.

Macroalgae have been shown to be relatively poor at nutrient uptake. I wouldn't point to success or failure based on macroalgae, unless we are talking about scads of it.

Ron

I may be ignorant, but can you explain how this reaction would take place in our tanks. Does macro algae produce energy in this sort of way? I only possess a laymen's knowledge of macro algae unfortunately.

The reaction of ATP to ADP (or its equivalent, there are several other minor pathways) has to occur to provide the energy for all cellular processes such as the synthesis of protein, the breakdown of other protein, replication of genetic materials, production of membranes... you name it, ATP (or more correctly the stored sunlight stuffed into the phosphate bonds) powers it.

Bacteria indeed do this process, in fact it was elucidated initially in bacteria. All life uses the process or variant of it to power every cellular process.

Macroalgae, cyanobacteria, diatoms and other microalgae all store energy sunlight in the form of sugars. To do ANYTHING they all break down the sugar and use it to produce ATP which is used someplace in the cell to perform a necessary function.

Given the importance of phosphate in these reactions, and within the genetic material (nucleic acids are largely built of phosphorus derived from phosphates) it is not stretching the imagination in any sense to say that phosphate are the single most important chemicals in any ecosystem - or tank...

Well, in the end, I guess the question is how hard is it to establish one of these sand beds?

Depends on whether you trust the advice of mythological being.

Not hard. It takes time, a few good innoculations, and the right basic sediments. The variety of organisms in such a bed is truly staggering as are the total populations.

I don't think there is a good source for sand fauna today in one spot. Although I have recommended several kits, I think these are starters. Additionally, a lot of fauna may come from fresh live rock.

the Inland Aquatics detritivore kit.... IPSF Wondermud

Both are okay - to get a hit of what you need. But consider that you have to assess the number of organisms in your systems that might prey on such tidbits (primarily fish, hermit crabs, and shrimps) and determine how, where, when or even IF adding such "booster" kits are worth it.

But even then one must have the proper sediment sizes. Is it accurate to say that if you have a regular crushed coral, live sand or SeaFlor sand bed that you are hosed?

No. A diversity of sand sizes is best. But you will get better results with about half of the volume of the sand consisting of what are referred to as "fines" - sugar fine sand and finer stuff. The larger stuff, 2+ mm, has problems that I have detailed in several posts and articles in print in the past, but basically it is too large for most animals to disturb and such disturbance allows detritus to be mobilized. Larger sediments allow the light to penetrate farther into sediments where they cause greater algal growth, but that may not be a real problem. Medium sizes are okay, but you get more critters per cubic unit volume with the finer sediments. Small sediment particles have much higher surface area to volume ratio and increasing this component of the sediment, by itself can stimumlate much more nitrogen utilization, and boost animal populations.

I started my sand bed using live sand with a bit of crushed coral and oolitic sediments. It is a pretty mixed bag of sediment sizes and has a population of animals in it now that is immense (from actual numerical sampling, I estimate the population of animals 1 mm or larger in my 45 gal lagoonal reef to be in excess of 800,000, and probably on the order of 1.5 million.

This system has been going for three years.

Otherwise, why would heavy feeding have gotten a bad reputation in the past.

Basically poor filtration and lack of the appropriate fauna.