I don't think I would say that I have a significantly different opinion of the ESV spray dried plankton after becoming aware of aquaculture studies on it -- I initially voiced my concerns about the lack of any information about the composition, the nutritional profile, and the method of preservation of the product. I think that those are all valid concerns and without any information upon which to evaluate the product, I certainly wouldn't feel comfortable recommending it to anyone. However, I am starting to have my concerns alleviated as we start to get some more information about the spray-dried plankton. There are a couple of studies of which I am aware that bear directly on this subject, but they fall rather short of being a "proper scientific study." In fact, I must admit that personally, I do not find these studies overly convincing because they are either unreplicated, suffer from poor experimental design or entirely lacking in proper controls. That aside, they *are* anecdotal evidence that the product certainly does merit further research and certainly may be a useful thing for reef tanks. There is more information slowly becoming available about the product as time goes on, and as I implied earlier, I have just had a long conversation with Bob Stark about this recently.

The study to which I think Richard is referring is the report of a shrimp hatchery in Penang, Malaysia, which reports survival of P. monodon increased from roughly 20-30% to 36% when switching from live algae cultures to the spray-dried plankton. However, there is no real information about the hatchery, the species of live phytoplankton used, etc., and there are no controls or replication that would add confidence to our acceptance of this report. In fact, 36% is not significantly different than 30% in a 2 sample test like this, so it is very hard to say that this is outside the realm of the normal variation of the system. It is obvious, however, that the spray-dried plankton did not perform *worse* than live algae in that particular case, and it certainly seems a viable alternative to live algae use for the culture of tiger prawns. Traditionally, Asian shrimp farmers would incorporate at least 50+% of the larval feed as live phytoplankton (the remainder being made up of a wide variety of cost-cutting prepared diets, including boiled chicken egg yolk, microencapsulated and microparticulate artificial diets, yeasts, fermented soybean cakes, and the list goes on & on...) because survival and production would drop significantly due to inappropriate nutritional content of the prepared foods and/or rapid deterioration and decomposition of the artificial foods in the culture vessel resulting in a rapid decline of the water quality and prolific bacterial growth. This is, of course, expensive and the introduction of spray-dried plankton is a real boon to these folks who are eager to replace the culture of live phytoplankton (usually some mixture of Skeletonema, Thalassiosira, Chaetoceros, Dunaliella, Nannochloropsis, Tetraselmis, and Isochrysis) with a simple and effective prepared food. For crustacean larvae the spray-dried plankton does seem to be a very cost-effective alternative to using live phytoplankton.

The two major concerns I had expressed about the product were

1. the nutritional value of the species of "phytoplankton" (I use "phytoplankton" in quotes because it is really a heterotrophic species more closely related to yeast than true phytoplankton) used in this product, and the effects of drying as a method of preservation -- especially given the research on urchin growth on live versus dried kelp (the earlier study I cited in which urchins grown on dried kelp actually starved while those grown on live stuff prospered), and
2. the clumping of the product and the resultant size of particles when resuspended.

The first concern seems to be largely alleviated with the release of the actual nutritional profile of the product

• Protein 39%
• Fat 32%
• Carbohydrate 13%
• Ash 12%
• Moisture 03%
• Fatty Acid Content (%w/w)
• Eicosapentaenoic acid (EPA - 205) 00.6%
• Docosahexaenoic acid (DHA - 226) 24.0%
• Vitamin C 321 mg/lb, etc...

There are reasonably good levels of amino acids, sterols, carotenoids, xanthophylls and the like to boot, so the nutritional profile of the plankton species used looks pretty good in comparison to some of the traditional phyotplankton feeds, and fantastic in comparison to the relatively poor alternatives commonly advocated for the aquarium industry (like Spirulina, pea flour and yeast-based "Invert food" products, etc.).

The biggest concern from the nutritional profile ought to be the low proportion of EPA in the product, although it is preferable to have a paucity of EPA than DHA because it is thought that most marine organisms can synthesize EPA from DHA but not the reverse. In fact, with one study of rotifer enrichment, this was found to be true (animals fed only the spray dried plankton had a higher than expected level of EPA although it was lower than that observed in animals enriched on Selcon).

For those of you that remember the original post, my concern about drying as a method of preservation stemmed from the urchin study I mentioned above. The nutritional effects of drying phytoplankton remain unknown, but given the results of the shrimp hatchery in Malaysia, it seems unlikely that a similar unexpected nutritional problem to that seen in the air-dried kelp will be found with the spray-dried plankton. However, I have seen reports of changes in nutritional profiles for Spirulina that has been "flash dried" (equivalent to spray-drying) as compared the live products, and there is no doubt that some compositional changes *do* occur during drying -- the question remains as to how much those changes matter to the final nutritional value of the product. Although the product may well be less nutritious after being spray-dried (as compared to live), it obviously does not become non-nutritious through this process as evidenced by the results of the shrimp hatchery.

However, I still have the same concerns about the product as I had originally voiced namely it performed very poorly in my tests. For the tests, I added 1 level scoop (40mg) of the powder to 20 ml of 0.2 um-filtered seawater and allowed it to hydrate for 5 min on a shaker table (about 100 rpm). I then vortexed the mixture at high speed for 30s before pouring it through a 183um mesh sieve, which retained 10 obvious particulate flecks of consolidated cells that did not dissociate during the hydration and vortexing. So I also tried mixing by sonication for 30s without any better results. Actually, the "pre-hydration" seemed to make the most difference in the resuspension of the stuff, rather than mixing for 30s or 2 minutes. In any case, I mounted 200ul of the vortexed slurry on a haemocytomer slide for counts and particle size measurements. Of the 148 particles that I measured, 81 of them were aggregations of cells rather than single cells, and the total particle size range among the mixed particles was from 1.5 - 452 um and the mean particle size was ~104 um.

In feeding trials with the larvae of 2 species of molluscs (the snail, Lacuna vincta and the nudibranch, Anisodoris nobilis) neither showed any significant growth (in fact there is potentially a significant decline in mean larval size over time, but I'll have to go back and actually do the statistics to answer that) over several days of culture until the larvae died at approximately the same time as sibling larvae that were maintained in 2-um-filtered seawater without any food being offered. I have not previously posted these results anywhere as I intended to include them in my WMC presentation along with the test results of the cryopastes and DTs phytoplankton, but it seems appropriate to give a sneak preview here. I think my original post went something to the effect of in experiments with the larvae of some local species that require phytoplankton to grow, I found that ESV's product did not perform well -- larvae declined over time and all eventually died without metamorphosing. In contrast, the DT's product and 2 of the Reed's cryopastes (Nanno & CHGRA) performed in a manner indistinguishable from the live phytoplankton I culture -- the T-Iso cryopaste, however, was also a poor performer (equivalent in terms of results to the ESV product), which makes me question their nutritional value...

I suspect that this could be entirely a size issue, and it is possible that the larvae I have chosen to use in my research were simply unable to consume enough of the aggregates of clumped cells to support themselves with the range of particle sizes I was able to obtain from hydrating and mixing the powder -- penaid mysis and post-larvae for which the spray-dried plankton worked so well thrive on particles larger than molluscan veligers. I don't think there has been enough testing on my part or that of the folks at ESV to convince me one way or the other yet that the product is a boon or a bust for feeding suspension feeders in reef tanks, and I really feel that the jury is still out on this product. I certainly don't think that it is providing a complete replacement for phytoplankton in terms of the particle size comparisons for animals adapted to feed on small phytoplankton such as Nannochloropsis, however, it obviously has nutritional benefits to animals (such as the shrimp larvae) capable of ingesting the larger particles sizes to which these cells clump during the drying process.

If it comes down to a decision about whether to use any commercially available "invert food" in a bottle, my recommendation will be for ESV's spray-dried plankton, hands-down -- if it comes to a choice between live phytoplankton and the spray-dried stuff for feeding animals that specialize on phytoplankton in the wild (e.g., Dendronephthya), my vote will be hands-down for the live stuff. If you have a wide variety of critters in your tank and are looking for a "general supplement" for feeding "suspension feeders" (in the general sense of the term), you probably can't go wrong by including a mixture of all the various products available and dealing with the relative benefits and drawbacks of each (which I think I have tried to explain in the past) as best you can...