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Rob Toonen

Phytoplankton feeding of reef tanks: Has the pendulum swung too far?


In the words of Rob Toonen:

I am a Canadian, born and raised in Edmonton, Alberta. If I had to pigeon-hole myself into a specific field, I would say that I am an Invertebrate Larval Biologist, but my interests are fairly diverse, and professional and personal research have been rather eclectic to say the least. I did my undergraduate degree at the University of Alberta, and my Masters degree in Marine Biology at the University of North Carolina, where I worked on the reproductive biology and larval settlement of tube-dwelling polychaete worms (Hydroides dianthus). Currently, I am a Ph.D. candidate in the Population Biology program at the University of California in Davis. Despite the fact that I study invertebrate zoology for a living, I still seem to spend a fair bit of time maintaining and writing about marine reef aquaria (rather than doing my research) as a result of my fascination with these animals. In the past, I have done research on jellyfish, corals, sponges, sea slugs, and polychaete worms, but currently I am working on larval transport and dispersal mechanisms in crabs.

My aquarium addiction started early; my dad owned a petshop when I was a child, and got me into fish keeping as soon as I was old enough to say I've had freshwater tanks as long as I can remember, and my dad helped me get started off breeding guppies about the age of 5. I've been keeping fish and trying to breed everything I can get my hands on ever since. Aside from maintaining over 30 tanks in my room when I lived with my (very tolerant) parents, I had a variety of aquarium-related jobs before starting my dissertation (from dolphin-trainer to managing the fish department of a local petshop, to a variety of independent aquarium consultant positions). I started keeping saltwater tanks around 1980, expanded into seahorses and reefs about 1985, and started trying to breed the animals in my reef tanks sometime in 1988-1989.

I have written numerous articles for online organizations including Reefs.Org and GARF, and frequent a variety of the marine aquarium list-servers and web boards online where many of my posts have been archived. I have written articles for several of the hobby magazines, including Aquarium.Net, Freshwater and Marine Aquarium Magazine, Marine Fish and Reef USA Annual, Practical Fishkeeping, and Tropical Fish Hobbyist, and I currently write a monthly question and answer column (Invert Insights) for Tropical Fish Hobbyist.

Anyone who has been following the various reef Bulletin Boards knows that there is considerable debate about the use of phytoplankton to feed coral reef tanks. Despite that debate, new phytoplankton products are being introduced to the aquarium market all the time, and the use of these products is rapidly becoming common-place among reefkeepers across North America (and I would guess elsewhere as well). As the use of phytoplankton becomes more common, the claims for it's usefulness in aquaria also seem to be ever more exaggerated, unfortunately. For example, I recently heard a pet shop owner telling a customer to start feeding phytoplankton to their LPS corals to resolve problems with coral bleaching in the tank - this recommendation came without asking anything about water parameters or tank conditions during the time the customer was describing the problems they were experiencing. This sort of grandiose claim for benefits of phytoplankton feeding naturally fuels opposition, and rightly so - phytoplankton is an important link in marine food chains, not a cure for whatever ails your tank! Tonight, I would like to discuss the role of phytoplankton in reef communities, what the benefits of including phytoplankton in your feeding regime are likely to be, and how to decide whether or not supplementing phytoplankton is right for your aquarium. I'll also try my best to sort of some of the confusion about what the big deal is all about and why there is so much disagreement over adding these tiny floating algae to reef tanks.

First of all, let me define what phytoplankton is. In the simplest terms, phyto means plants, while plankton means tiny particles floating in the ocean - put it together and phytoplankton is simply a fancy word for tiny floating plants (such as diatoms and dinoflagellates). These tiny plants serve the same role in the food chains of the oceans as grass, shrubs and the like serve on land; namely, small herbivorous things eat them, and are in turn eaten by bigger things and so on down the line. Phytoplankton form the basis of many, if not most, marine food chains, and ultimately almost all visible life in the ocean is supported in one way or another by phytoplankton.

Next, let me start with saying that I think a lot of the debate over the use and benefits of phytoplankton for feeding reef tanks comes from people being unclear about exactly what the topic of discussion is. Before any reasonable discussion can take place, it is important to define some terms and outline the scope of the questions to be discussed. Before you can make any decisions about what is best for your aquarium, you first have to determine what the goals are for your aquarium, and what philosophy of aquarium keeping you plan to follow. For example, are you trying to maximize the diversity of critters in your aquarium, are you trying to minimize any potential problems with nutrient export, or are you aiming for a happy medium? Are you trying to recreate a particular reef habitat and incorporate as many of the organisms as possible from that habitat into your aquarium, are you trying to create a pretty collection of animals from around the globe that catch your eye at the LFS, or are you trying to generate the perfect set of conditions to maximize the growth of a couple of specific species, such as Acropora or Montipora? Depending on your answers to these questions, the decisions that you should arrive at with regards to feeding will likely be quite different, and if you have never given any thought to such issues, I would suggest that you do.

OK, so having gotten that out of the way, lets define the scope of our discussion here. The first question to address is simply whether or not to feed your tank at all. If we accept that there are likely to be benefits of feeding a tank, and decide to do so, the next question becomes what type of food to feed. Assuming we can decide on what to feed, we are then faced with assessing the different options available to decide what are the specific pros and cons of each source of that food item available, and how much to feed. This again involves deciding exactly what we are trying to accomplish by feeding, and then assessing which of the available products provides the best value, or nutrition, or ease of use, or whatever else you deem most important to your particular situation. To accomplish that, we need some controlled and objective manner with which to compare the various products on the basis of value, or nutrition or ease of use, etc... I can't possibly do justice to all these topics in one talk, so I'm going to try to give you an overview from which you should hopefully be able to draw your own conclusions about whether or not phytoplankton feeding is right for your tank.

Let's start off with the first question: should you feed your tank? Everyone realizes that to keep fish healthy in an aquarium, they need to be fed something, but many people are misled into thinking that feeding their corals, clams or other animals with photosynthetic symbionts (such as zooxanthellae) is somehow going to be bad for them. It is true that animals with photosynthetic symbionts have forged a relationship that makes it easier for them to survive in the nutrient-poor tropical waters that support most coral reefs, but it is untrue that these animals do not require any nutrition other than that provided by their symbionts. The fact that no organism on a coral reef can obtain 100% of their nutritional requirements from the release of photosynthate by algal symbionts is viewed as support for the importance of additional feeding by many, but other people point to the exact same data and say that numbers like 90% are so close to self-sufficient that no intentional feeding should ever be necessary. It gets even more complicated when we realize that both feeding and photosynthetic output are related, and that studies with corals in captivity have shown that direct uptake of dissolved organics seems to occur only in starved animals and not in fed ones, and that the rate of photosynthetic output by zooxanthellae actually decreases when their host is starved. It is safe to say that the consensus of studies in natural reef communities have shown time and again that all coral reef animals, including those that house photosynthetic symbionts, feed in nature, but that does not address whether or not there is sufficient incidental feeding in the average aquarium (through such things as fish feeding and wastes, reproduction of tank-mates, and/or capture of plankton such as copepods, mysids and amphipods from the aquarium) to eliminate the need for intentional feeding of corals and other reef inhabitants in an aquarium. The problem is that there will likely never be an absolute answer to the debate about whether corals are effectively self-supporting in aquaria (almost certainly the answer depends on the tank and system in question), and the choice is ultimately up to you as an aquarist to decide whether or not to feed them in your aquarium as well.

Most of the animals on a coral reef are very effective at capturing either zooplankton, phytoplankton or both from the water that passes over them. Many of these animals can (and do) capture phytoplankton directly, and the ones that cannot (such as the fishes) still take advantage of the nutritional quality of these tiny algae by preying on small animals that do eat them (such as copepods, rotifers and mysids). Why? Because there are a number of essential nutrients provided by marine algae, especially phytoplankton, which cannot be synthesized by animals, and are therefore extremely important components of a healthy diet.

The most important of these nutrients are the class of lipids known as long chain Omega-3 fatty acids. I won't discuss this in detail here, but suffice to say that these nutrients come almost exclusively from marine algae. One of the major breakthroughs in the aquaculture of marine animals was the discovery that these fatty acids were an essential part of the diet, and without them, nutritional deficiencies or arrested development are still common problems.

Despite the fact that phytoplankton form the basis of marine food webs in general, and are an essential component of the diet for many reef creatures (such as fan worms, sea apples, giant clams, gorgonians and tunicates, to name a few), they are probably the least common element included in feeding an aquarium. It is easy to feed flake, freeze-dried or frozen prepared foods to the fishes and large invertebrates in the aquarium, and virtually every aquarist does so. It is much harder to provide nutritious particles the size of phytoplankton (on the order of 1/100-1/500th of a mm in diameter), and that's why many people are excited that these products are now available to the average hobbyist to feed their aquarium at home. To me, the simple facts that all animals need some food, that there are many coral reef animals that feed on particles far smaller than any provided by typical fish foods, and that these tiny floating plants provide essential nutrients and form the basis of most marine food webs is sufficient to make me want to supplement them in my aquarium.

But, is phytoplankton feeding right for your aquarium? If your answer to my question about your goals in keeping a reef aquarium was along the lines of maximizing diversity or recreating a particular reef habitat type, then there are volumes of research showing that phytoplankton plays an important role in supporting natural reef ecosystems. If your answer was more along the lines of minimizing potential problems with nutrient export and maximizing growth of Acropora, however, you're unlikely to see much visible benefit (and potentially cause yourself more problems) by adding phytoplankton to your aquarium. Having said that, however, I must also say that I suspect that we'll soon see a change in the standard dogma that stony corals are incapable of capturing and ingesting phytoplankton (a legacy of Yonge from the '30s), because more and more field studies are finding the gut of many corals (including SPS and LPS, in addition to soft corals and gorgonians) contain phytoplankton. For example, some research papers coming out of Australia recently have shown that corals like Goniopora and Heliofungia have a more phytoplankton in their guts than would be predicted from any "accidental" capture at the rate these tiny algae are found in the water column above them. In fact, one of these researchers went so far as to propose that most corals capture and ingest phytoplankton, and this may prove to be an important source of nutrition if we can shed the baggage of 70 years of stubborn refusal to examine the data.

If you're willing to accept this premise that phytoplankton is an important component typically absent from traditional aquarium keeping at home, then we can assume that you have decided to feed phytoplankton to your aquarium, and move on to the next question - what do you want to feed & how?

Again, as I mentioned above, it is simple to provide a surrogate for moderately-sized particles such as zooplankton in a reef aquarium, and the feeding of frozen brine shrimp, copepods and mysids is relatively common among reef enthusiasts. However, neither the particle size nor the nutritional content of phytoplankton is easy to recreate in any artificial food product, and even dried forms of real phytoplankton suffer in terms of particle size relative to the live cultures (I'll come back to this in a while). Unfortunately for us as aquarists, the feeding mode of many reef animals does not allow them to capture anything but these tiny particles, and in order to keep such animals in an aquarium, those foods must be available. Again, I would emphasize that it is not necessary to feed a reef aquarium on phytoplankton, and there are plenty of people who have been keeping beautiful reef tanks without feeding for a long time, but there are many animals on a typical reef that require phytoplankton to survive and there are plenty of others that are likely to benefit from the addition of such tiny food particles.

OK, so assuming that your plans for your tank are likely to be helped by phytoplankton feeding, and you have decided to do so, there are a variety of options currently available: live phytoplankton cultures, Instant Algae pastes (frozen), spray dried, and preserved liquid room-temperature forms. Each has distinct advantages and disadvantages, and it depends on your tank set up, and what you're trying to accomplish which product is likely to be best suited to your tank I'll try to briefly cover some of the advantages and disadvantages of each.

Live phytoplankton is obviously the best option in terms of nutritional value and low risk of over-feeding. Live cultures are the standard by which all other products are judged, and the others can be "as good as live" but no one has ever discovered a phytoplankton supplement that performs better than live. An additional benefit is that live phytoplankton, unlike dead products, can actually take up some nutrients while being fed to the aquarium, and it is almost impossible to foul an aquarium through the addition of live phytoplankton (I said "almost!"). Currently, live phytoplankton cultures are available from suppliers such as DT's Phytoplankton and LiquidLife USA. The down side to using live cultures is that some retailers mishandle the product, intentionally or not, which significantly decreases its nutritional value, and may actually kill the phytoplankton leading to potential fouling problems. Unlike the preserved products, there is nothing to slow bacterial growth in a formerly live culture gone bad, and when it goes off, it gets rancid very fast! There have now been a couple of reports of people crashing tanks by adding noxious phytoplankton culture that has decayed in the bottle, and if your retailer tells you something like "live phytoplankton only needs refrigeration after it is opened," my advice would be to look for another place to buy your cultures. Even live cultures need to be refrigerated as soon as they are no longer actively growing, or the cells decrease in nutritional value and potentially crash quite quickly. Storage in the refrigerator may or may not lead to problems in the home (such as the complaining spouse syndrome, or house-guests thinking it's Wheatgrass or some other nasty health food concoction and guzzling some ), but it is the best way to preserve the nutritional content of the product after it is removed from the culture conditions. The other major drawback to using live phytoplankton is that it is the most expensive of the options for providing phytoplankton to your aquarium.

The second option is the cryopreserved Instant Algae pastes from Reed Mariculture. The frozen pastes provides a less expensive and equally nutritious source of phytoplankton, again provided that it is stored correctly (e.g., see my "Storage of cryopaste" article in the Reefs.Org library). The best bet out there right now for this type of product is the Tahitian Blend from Brine Shrimp Direct (BSD) - it is a mixture of a number of different phytoplankton species of various sizes and nutritional profiles that provides an excellent choice for a general supplement for a reef tank. The primary benefits of using the Instant Algae paste are the low cost relative to live cultures, and the diversity of algal species and particle sizes that can be included in a mixed phytoplankton product like the Tahitian Blend. The drawbacks to this method of phytoplankton feeding include: 1) the algae are dead, and as such are equivalent to adding any other food such as frozen brine or flakes to your tank - if it is not eaten immediately, it will begin to break down, decompose and degrade water quality in your aquarium. 2) Aside from the fact that uneaten food will degrade in the tank, these products are extremely concentrated, which is a plus in terms of cost effectiveness, and a big minus in terms of people's tendency to over feed. If you have a problem with nutrient accumulation in your tank, or have a habit of overfeeding to start with, then this is the option most likely to cause you problems down the line from dumping too much food into your tank! 3) The stuff needs to be kept in the freezer, and the colder the better. It keeps quite well in a - 40C freezer, but the average refrigerator freezer maintains about - 20C, and at that temperature (especially with frost-free freezers), the storage life of the phytoplankton is on the order of about 6-8 months before there is a significant decrease in the nutritional value of the product.

Phytoplankton can also be preserved by drying, and the Spray-Dried Marine Phytoplankton (SDMP) from ESV is the primary choice here. Some of you may have seen me question the value of this product when it first came out because there was no information available about either the exact content or nutritional profile of the product. That information has now been released, and the product is actually very good in terms of nutritional profile (see my recently updated Spray Dried Phytoplankton article in the Reefs.Org library for more detail), and it is a very cost-effective and easy to store alternative to the products above. However, the major drawbacks with this product are that it does not generally provide particles of the size range of the majority of phytoplankton, and that it requires mixing in a blender prior to feeding in order to get any particles of the correct size range. There are 2 issues that lead to problems with particle size here: 1) storage at room temperature (especially with higher humidity) causes irreversible clumping of some particles such that they more closely approximate the size of rotifers than phytoplankton over time, and if you pick up the product from the shelf of the local petshop, chances are that it has started clumping before you even bring it home. 2) Even if you bought the stuff fresh and stored it in the freezer, however, the method of mixing is very important to the final particle size, and requires that you mix it with a blender for 2 minutes (as suggested by the company) to get the correct range of size particles to be useful as phytoplankton. If you tend to mix it by hand, dump it into a powerhead stream or any of the other less vigorous methods I have heard people mention as their "trick to mixing ESV" then your particle size is almost certainly too large to provide phytoplankton to your tank, and most likely provides a better size approximation to rotifers (again, I discuss this in detail in the Spray Dried Phytoplankton article in the library). Depending on your aquarium, however, this may actually prove a benefit rather than a detriment, and many people feed a combination of both the SDMP and a live or frozen phytoplankton food to cover a larger size range of particles for animals such as gorgonians and the like. Another alternative food product in this zooplankton size range are the "cluster" and "rotifer" classes of Golden Pearls (available from Brine Shrimp Direct).

The last group of products are those that are preserved in some way to be stored at room temperature and sold as a liquid phytoplankton supplement from the shelf of the local petshops. These products include Kent's Phytoplex and TLF's Marine Snow among others. The obvious benefit to these products is that they are easy to obtain, store and feed, but on a per feeding cost, may actually be more expensive than some of the other phytoplankton products out there. The fact that these products are only available to the retail pet trade, and have been largely ignored by the aquaculture industry should be some indication of their relative value, but I wanted to look at how well these products compared to the options listed above. I have been doing some new testing of the various phytoplankton products for my presentation at the next Western Marine Conference (WMC) and the best performer of all room-temperature shelf products by far (in terms of preservation of the phytoplankton) was the TLF product Marine Snow. In fact, I was so surprised at how good Marine Snow looked relative to the other products that I repeated my tests to make sure that there hadn't been a mistake somewhere! I am pleasantly surprised and encouraged by my results so far, and I hope to expand on them for my presentation at WMC 2001 in Monterey. In any case, I would say that based on my results thus far, this was the only product worth serious consideration from this group, and if you've seen the online discussions about Marine Snow (e.g., search the discussion board archive), and are not impressed with it, well...

Ok, that is a really brief overview of the available products and what I think are the major pros and cons of each. Which product will best suit your needs will again depend on what you are trying to accomplish in your aquarium, and what factor or factors (price, storage, ease of use, potential for overfeeding, etc.) is most important to you. I have previously discussed my data on larval growth as an objective means of comparing the various products, and again more detail on this topic is posted in the library archives, but the statements that I have made above about nutritional value and performance are based on these data. Insofar as larval growth and survival provides a ruler for the relative usefulness of each product, my comments about each product are the essence of my presentation at WMC this past summer (where I finally got to meet a bunch of you). For those of you that feel uncomfortable with the use of larval growth data as a metric of phytoplankton performance for reef tanks, I can only say that my guess is you're never going to see any more realistic data set for the use pf such products in an aquarium. The larval growth studies I performed took almost a full year to complete, and although people have criticized my tests for being overly simplistic, and not dealing with the growth of corals, or "reef tanks" as a whole, these growth comparisons remain the only objective test we have for the relative nutritional value of the various phytoplankton products on the market. Such tests are certainly oversimplified (feeding larvae in a plain glass jar instead of a community in a reef tank), but they were incredibly work intensive even as simplified tests, and until someone undertakes the monumental task of doing a properly replicated and controlled feeding test on entire reef aquaria (which I doubt will ever happen), the larval feeding trials are the only objective means we have to examine the claims of the various manufacturers of these products.

The fact is that studies of nutritional requirements and diet are rare for marine organisms, and even for humans such studies are vague enough that there is no general consensus among the experts for what is the "ideal" diet - every year there is a new best-seller diet fad by someone touting the benefits of the newest dietary strategy like eating foods based on the fat or carbohydrate content of foods, or your ethnicity, or even your blood-type. Given the amount of study and money thrown at human nutrition, if a single acceptable answer cannot be found for the "ideal" diet for us, how likely is it that we'll get a concrete answer for some slimy marine invertebrate?

I argue that there is plenty of evidence that all the animals we keep in our reefs feed actively in the wild, and that nutrients provided by phytoplankton are essential to the normal health and development of marine animals studied to date. Given the interest in this topic, and the number of questions generated by it on a regular basis, I have to guess that others feel the same way. However, given some of the conversations that I have had or heard of recently, I think that many novices have been simply told that they need to feed phytoplankton if they want a reef tank, or that phytoplankton foods will cure whatever problem they have with their tank (such as the coral bleaching example I mentioned above). Such claims are, quite simply, untrue and I think that the widespread use of phytoplankton (at least among aquarists in the online community) may actually be starting to go overboard. I have seen discussions in which people brag about the amount of phytoplankton they feed their tanks, and questions about who feeds the most phytoplankton. This is silly, folks! I've tried to give some detailed accounts of what the cell concentration per ml of tank water ought to be according to research on clearance and growth rates in the lab a number of times in various places, and - the addition of ReefCentral's algal feeding calculators are designed to help people figure out what the maximum amount of phytoplankton required to feed the average tank is likely to be, and how to slowly ramp feeding up to that amount. There is no minimum - the minimum is the traditional amount of "I've never even heard of phytoplankton." People who have known me for long enough will realize that I've been advocating phytoplankton feeding since the days that RAMR was the only show in town , but I just wanted to clear the air here - phytoplankton is a food item. It is not a miracle drug or cure for whatever ails your aquarium, and although there will certainly be specialty tanks that require higher feeding levels, the amount of phytoplankton you want to dose into an aquarium ought to always be "just enough."

I also want to take a moment at the end here to really make it clear where I am coming from in terms of these discussions. What I consider a "reef tank" has a wide diversity of animals contained in it - coral reefs are beautiful and interesting because of the amazing diversity of species supported in such a relatively small area. To me, that is something worth paying attention to and trying to recreate in my own aquarium, and diversity, as it's own reward, is a goal for keeping a "reef" as opposed to a "fish" or "coral" tank. Some opponents to phytoplankton feeding have claimed that these recommendations are circular: that I advocate a design based on deep sand beds (DSB) and supplemental feedings - to paraphrase this argument: you say we need to feed to support the diversity of critters in our DSB, but we need the critters in our DSB to help deal with the excess nutrients generated from supplemental feeding.

That is not the point I have been trying to make at all. My personal view is that I want animals in my tank that are reliant on nutrition other than that provided by the zooxanthellae. I want to maintain a high diversity in my tank - diversity is not an excuse to feed my tank, it's a goal of having a reef aquarium in the first place. My argument here is simply that there are an entire suite of animals that depend on microscopic planktonic foods for survival, and that essential part of marine food webs has traditionally been the least available for feeding of animals in the home aquarium

without that microscopic planktonic food many obligate filter-feeders will obviously be less abundant, if they are present at all, yet these animals are a common and important part of natural reef communities. That amazing overall animal diversity is the thing that makes coral reefs unique among marine habitats, and the argument to avoid diversity so that we don't have to feed our tanks, or to reduce this meaning of reef tank to corals (or more specifically SPS corals, to some) seems, quite frankly, narrow-minded to me.

So with that, I hope I've explained where I am coming from in discussions such as these, and at least made you think about where you are coming from in this matter. For those of you who are interested in the use of phytoplankton as a supplemental food in your reef aquarium, I hope that I've helped you through some of the murk surrounding the use of phytoplankton in reef tanks, and explained what the pros and cons of the various products are (and some of what they are not).

Thanks for having me! Rob

Now's time for the Question and Answer session!

Do you think acros can benefit from phyto. I assume that they cant due to the size. Any thoughts?

The standard dogma is that stony corals cannot capture phytoplankton, and even those that do by accident cannot digest it. This comes from work that is coming under question more and more as people find that corals (both SPS and LPS) have phytoplankton in their gut at a rate higher than that in the water around them. The 2 possible explanations for this are 1) they capture it because they like it, or 2) when it ends up in their guts and they can't digest it, it hangs around so long that it looks like (1). No one knows the answer to that yet, but there is currently no evidence to suggest that Acropora or other stony corals capture and digest phytoplankton. So to make a long answer shorter, there is no reason to expect a benefit to Acros from phytoplankton feeding...

I've actually seen my acropora polyps catch and take in food as large as adult brine shrimp. Is it that phytoplankton is too small for them to catch, that they get it higher up the food chain, or perhaps that it's not a part of their diet?

I don't think it's too small for them to catch, because one of the studies I mentioned from Australia found Heliofungia with high proportions of phyto in their guts. If Heliofungia can capture phyto, any coral ought to be able to...

There are many types of phyto, do all have omega-3?

Yes and no. Most have some ability to manufacture Omega-3, but it depends on the species, and the culture conditions whether or not they do. Some, like Spirulina, have none no matter what you do, but all the species commonly available in the pet trade have reasonable amounts of Omega-3 if cultured properly...

Are there any circumstances when phytoplankton would naturally occur in an aquarium?

Sure - every time you scrape the diatoms off your glass, you have in effect a "phyto bloom" It's just not possible to maintain cell densities on the order of 10,000 cells per ml or so in any reef aquarium I have ever seen. If you did, you'd probably be looking for a way to clear your gross green water

Is it possible to buy a bottle of DT's and use the phytoplankton enclosed to start a culture, or is it necessary to purchase a live culture from inland aquatics, IPSF, or other such locations?

Nope - it is easy to start a culture from DT's and it's even possible (if you're lucky) to start it off some of the newest Instant Algae pastes. It's not the source of the phytoplankton that matters, it's how it's cultured. The same species of phytoplankton can be extremely nutritious, almost useless, or even downright toxic depending on how it is cultured and when it is harvested. I have a greenwater FAQ on the web that describes what is involved in growing your own phyto cultures at home, and although it's not expensive or particularly hard, it is more work than it's worth to me, and I buy mine...

What are your opinions on feeding clams. Daniel Knop sugessted in his book it was a good idea. But in an article in the library he doesn't think that Crocea or Deresa feed on phytoplankton.

I just sent him a message asking him why he said that. There is plenty of data that show clams feed, even crocea and derasa. It's just that phytoplankton filtration only accounts for about 10-20% of their energy budget as opposed to 40% or so in some of their cousins, and up to 100% in T. gigas. I think that comment really meant "it's more hassle and potentially dangerous than it's worth" not "they can't feed." I asked him if we can post our offline exchange onto that article when we're finished our discussion, and hopefully he'll agree...

What are your opinions on adding nitrate to the tank for clam which are bleaching due to lack of nutrients to maintain the zoox. would it be better to feed the clams with phyto?

There are lots of reasons that could lead to a clam bleaching, and starvation is only one of them. If you're positive that the cause is nitrogen starvation, then phyto should help. If you're not, and it happens to be one of the clear water species that have little reliance on heterotrophic feeding (phyto filtration) then you could actually make things worse rather than better by adding particulates to the water that could clog their gills. It's just so hard to say what the ultimate cause of decline is in invertebrates

how can you decide what "disease" they have when the only symptoms for them all pretty much boil down to: 1) bleaching, 2) clamping or 3) sudden necrosis? I just don't think it's possible to make blanket statements about how to treat things based on something common like bleaching -- it could just as easily be temperature, nutrient, light or post-shipping stress as starvation...

How can you start a culture from pastes when the algae are heavily centrifuged and then cryogenically frozen? Wont that lyse the cells or kill them totally

It better not lyse them, or you're left with pure nutrients added to your tank rather than phytoplankton. The truth is that it does kill the vast majority of the cells, but some do survive, and even more so in the new line of refrigerated "pastes" that should be available in the next month or so from BSD. It's not easy to do, but storage of difficult cells lines to restart cultures was the reason that the techniques used by the Reeds were first tested by phytoplankton researchers...

You mentioned the problematic clumping of spray dried phytoplankton and how to reverse the process with the blender, but what about the benefits of the larger clumps? I've noticed that my fish will eat them, and usually break them up in in the process. Would you consider this beneficial to the tank overall, compared to having one small particle size?

Two things

1) the clumping does not seem to be reversible by blending. If you check my data posted in the library on this subject, it shows that particle size increases with time or incorrect mixing method, and does not revert once it is clumped. 2) Absolutely, and that's why I said that a combination of the feeding SDMP with another phytoplankton product is likely to be a benefit rather than a detriment. Especially for tanks with a variety of animals, you're covering a greater size range, and the Omega-3 concentration of SDMP is one of the highest ever tested... (DHA in particular)

Do you prefer mixing a blend of live, instant, and spray dried phytoplanktons, along with the golden pearl clusters/rotifers in one feeding, or alternating feedings of each product? can you elaborate?

It depends on the tank

at home with my own aquarium, I alternate. At work, where I have several reefs and one is a large display tank, we mix all the products together and dose them simultaneously. I use both the SDMP and golden pearls as a "rotifer" replacement rather than a phytoplankton replacement. Then we dose phytoplankton at the appropriate amount to get a final concentration of about 10,000 cells / ml every second day. I don't consider this ideal, and it's not what I do at home, but it's easier and I think it's better than nothing. At home I feed phytoplankton at 10,000 cells / ml every morning and then rotate a blend of SDMP, golden pearls and enriched baby brine about an hour later....

Did your analysis of TLF Marine Snow analyse the nutrition provided by the product or just the degradation of the phyto in the product?

I just did the phyto breakdown curves because the work to do the growth experiments is just more than I can handle by myself. I wish I had the free time (or dedicated student volunteers) to do these experiments for every product that is out there, but I just can't. That leaves the phyto breakdown curves (which correlate perfectly with the larval growth curves, BTW) as the quick-n-dirty way to assess product performance. I will say that for all the talk about how Marine Snow is nothing but water, there was at least as much particulate matter in it as any of the other shelf products I tested, even though on a per ml basis, it was much more dilute than some of the others...

Where are the results from the larval feeding experiment published?

They are not. I presented them at WMC and was writing them up to submit to the journal Aquaculture, but the hobby mags don't really like to see the name brands included in the articles, so I haven't done much beyond finding that out...

Have any studies been done to check how long phyto resides in corals' (not just Acros) guts before it is digested or excreted?

Not that I'm aware of. I can try to check, but as far as I know, this is pretty new territory that has only opened up again since the Dendro story hit the presses...

What do you suggest what corals would benfit most from phytoplankton shrooms, stonies, what ?


there is good evidence that these guys are capturing and using phytoplankton a lot, and even the "photosynthetic" ones seem to capture a lot of phytoplankton. I think that a number of soft corals are likely to fall into the same category when/if the studies are done, and I suspect that a number of SPS like Agaricia are probably capturing phyto as well. At this point, though, it's pretty much all guessing when it comes to phyto and corals, unless you're talking about Gorgonians or Dendros.

Would the scraping the glass be enough to help support a smallish aquarium in the long term?

This may sound simple, but I have to ask "enough" for what? If you mean for a sea apple, or flame scallop, then the answer is certainly no. If you mean for a little extra nutrition in the tank and the odd particle being captured by a photosynthetic gorgonian or the like that does not really need it, but would like to have some phyto, then the answer is probably yes. I guess it all comes back to your goals again, and you're really the only one who can answer that....

Well, that is it for the questions and the formal part of the meeting. Thank you very much Rob for taking the time out to talking to us tonight. It is very much appreciated.

Created by liquid
Last modified 2005-02-07 05:56