Most of the general info in that article is species dependent.
While numerous publications & studies about the use of probiotics and/or prebiotics in aquaculture have emerged during the last decade, we still know very little about their use regarding the vast amount of ornamental species of fish found in tthis hobby.
Here's what we do know.
There are numerous strains of probiotic bacteria, each targeting different types of aquatic pathogens. In order for any of these probiotics to be fully effective, they must be in a live form, or able to be reactivated once in the GI tract of the host. The vast majority cannot survive the heat, moisture, and pressure during the processing stage of commercial food manufacture. Bacillus species such as B. subtilis and B. licheniformis are commonly used as probiotics in aquaculture, but studies have shown that if added before the extrusion, expansion, or drying process, it will result in the loss of 99% of the Bacillus spores. In order for probiotics to have any type of positive effect on the fish, they must survive in very large quantity.
One workaround is for manufacturers to add these live microorganisms after the food is processed, in a dry powder form. Previous studies have indicated that only 60% of probiotic bacteria remain viable when applied in this manner, and viability is reduced by another 25% within 12 months of the date of manufacture. (even more so if stored under less than ideal conditions)
To make matters worse, tests that have been performed in the past on numerous pet & human food products by researchers at the Ontario Veterinary College (as well as other accredited institutions) that were sold as containing "probiotics" had results that were far from being impressive. Many of these organisms were improperly identified on the label, a large percentage of products did not contain the specified organisms, contained other species of organisms, did not contain the stated numbers of organisms, or if numbers were stated they did not guarantee that the stated number would be present at the time of expiry.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC340078/
"Because probiotics are considered food supplements, not drugs, there are no regulations regarding their use as supplements or food additives. Various studies have reported that quality control among probiotic supplements intended for human or animal use is poor, with a significant percentage of products either not containing the organisms stated on the label, not containing the numbers of organisms stated on the label, or containing additional species. "
"Overall, commercial pet foods that claim to contain probiotics appear to contain very low numbers of viable organisms, and often do not contain the species listed on the label. Whether this relates to improper addition of organisms during processing, failure to survive processing, or poor viability during storage is unclear. Regardless of the contents of any diets containing lactic acid bacteria or bacilli, it is debatable as to whether they should be considered to contain probiotics without demonstration of species-specific efficacy."
More info from the OVC can be found in the following link
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC340366/
The link below offers more information on this subject with regards to the use of probiotics in aquaculture:
http://mmbr.asm.org/cgi/content/full/64/4/655
Most of the literature references on the use of probiotics report on probiotics consisting of single bacterial strains (Table 1). It stands to reason that probiotics based on a single strain are less effective than mixed-culture probiotics when microbial control is desired. The approach should be systemic, i.e., based on a mixture of versatile strains capable of acting and interacting under a variety of conditions and able to maintain themselves in a dynamic way. It has been argued above that in aquaculture the microbial habitat undergoes continuous alterations, allowing constant changes in the structural composition and the functions of the microbial community. It is unlikely that a single bacterial species will be able to remain dominant in a continuously changing environment. The probability that a beneficial bacterium will dominate the associated microbiota is higher when several bacteria are administered then when only one probiotic strain is involved.
Probiotics are usually defined as live microbial feed supplements which beneficially affect the host animal by improving its intestinal microbial balance (Fuller, 1989). Based on this definition, probiotics may include microbial adjuncts that prevent pathogens from proliferating in the intestinal tract (Gatesoupe, 1994). Most probiotics proposed as biological control agents in aquaculture belong to the lactic acid bacteria(LAB). But LAB has some limitations due to small antibacterial spectrum. These activities normally inhibit only closely related species of gram positive microorganisms (Suma et al., 1998). However, almost all the pathogens involved in aquaculture are gram-negative bacteria. Bacillus subtilis, a gram-positive, aerobic, endospore-forming bacterium, would fall under this category, yet this is exactly what one of the major fish food manufacturers has listed in their ingredients as their probiotic. Hmmmmm.
These live microorganisms must then be able to survive transit through the acidic environment of the stomach and resist bile digestion. Organisms that survive the acid and bile must possess a number of other properties, including the ability to adhere to intestinal epithelial cells, colonize the intestinal tract, produce an antimicrobial factor, and inhibit enteric pathogens. In other words, unless the probiotic supplementation meets ALL of the requirements above, it's effect on the health of your fish will be minimal, if anything at all. In fact, depending on the microorganism used, if supplemented on a constant long term basis it could even prove to have a negative effect on the health of your fish.
At this point nobody knows what if any long term effects some of these microorganisms may or may not have on the long term health of any species of fish, as no long term studies have yet to be performed. (and most certainly not on any tropical fish species) Commercial fisheries tend to focus on short term feed trials, and short term results, as fish that are raised for human consumption typically aren't being kept long term.
The part that I find most alarming about products used in aquaculture is that probiotics and/or prebiotics may be marketed without any demonstration of efficacy or safety. None. Personally I don't find that very comforting.
Currently the USA based Center for Veterinary Medicine (CVM) will not even allow any type of health or disease claims on a pet food label that lists probiotics. (dog, cat, fish, etc)
Some fish food manufacturers have made claims about their use of probiotics for the reduction of solid waste in the aquarium.
This is certainly not a new concept in aquaculture, these same type of products have been manufactured for the use in septic systems for decades, and there are a number of aquatic related companies that have been marketing these same types of enzymes & micro organisms for just as long. Below is the description given for one of these products that is marketed for reptile use. (company & product name has been removed/replaced with XYZ.
Eliminates organic waste build-up in gravel, filters and on submersed surfaces Reduces odors Solubilizes organic waste. XYZ helps eliminate organic waste in reptile habitat water parts. (e.g. turtle aquariums, snake bowls or amphibian water parts). It efficiently reduces solid waste and leftovers in the water from overfeeding. Use XYZ to complement filters for beneficial bacteria build-up and to reduce odors associated with decaying waste. Solubilized waste becomes a food source for beneficial bacteria introduced by adding XYZ. XYZ includes 4 strains of micro-organisms, selected for their ability to biodegrade proteins, fats, carbohydrates and certain hydrocarbons. Only contains Class 1 micro organisms, which are classified non-pathogenic. Bacterial Community Includes: Bacillus amyloliquefaciens, Bacillus subtilis (2 strains) and Bacillus licheniformis.
While these products may very well solubilize organic waste, all that is required to remove organic waste, is a water change!
Yes, good old fashioned water changes, filter maintenance, and substrate cleaning is all that's required, what a novel idea! Through regular water changes, filter maintenance, and substrate cleaning one can keep their tank in perfect balance with the bio load. Not only does regular maintenance remove solid organic waste, this will also remove dissolved organic compounds (DOC's), and just as importantly, it will replenish minerals & trace elements in the water that become depleted over time.
These simple basic maintenance steps are what is involved in helping to promote a healthy aquarium, and no fancy shmancy bacteria in a bottle (or pellet food) product is going to change that. Perhaps the fish food manufacturers that feel their products require added bacteria to break down all of the solid waste produced from eating their food, should spend more time & resources utilizing higher quality raw ingredients, that have higher rates of digestibility, and less starch. Hmmmmmm.
In commercial applications, such as large intensive fish farm settings, the study & use of probiotics is to control pathogenic bacteria by improving water quality by balancing the bacterial population in the water, and reducing the pathogenic bacterial load. Unfortunately these bacteria are known to evolve very quickly, with resistant strains in some areas, it has been suggested that some of these even being resistant to probiotics.
In "farmed" fish there may be a more limited range of parasites found compared to what is present in the wild, but they are often present in far greater numbers. Hosts are readily available in farm conditions where fish are raised in large numbers, which allows parasitic infestations to grow with no natural check or balance in place. In an aquarium setting, this is typically not an issue.
IMO if you want to stimulate the immune response of your fish, and keep it healthy long term.
1. Feed a high quality, highly digestible premium diet to your fish where all of the nutrient levels exceed the minimum requirements for the species, including all of the various vitamins & minerals. While ingredients such as Spirulina, Garlic, Seaweed, Micro-Algae, are not considered true probiotics, as they are not "live" organisms, they do in fact contain bioactive compounds, that have been proven to have a probiotic effect on fish. Some of these compounds have been shown to have biological effects in fish such as growth promotion, immunostimulation, anti-stress, anti-bacterial, anti-fungal, anti-virals, and appetite stimulators.
2. Keep your water & filters in proper condition (limiting the number of pathogens) If your stocking density is high, then be prepared to perform the required maintenance to keep conditions stable, and water quality high.
3. Keep the overall environment for your fish as stress free as possible.
While I applaud the commercial aquaculture circles for seeking alternative routes to treating fish pathogens via more natural methods, the reality is they are now only doing so due to their own large scale & long term abuse of medications such as antibiotics. Anyone that has read my write up on treating internal protozoans (spironucleus sp) via an oral 3% magnesium sulphate solution knows that I am all about using alternative treatment methods whenever humanly possible, but in the case of probiotics I don't believe that hobbyists need to supplement live microorganisms in order to keep healthy disease free livestock. Simple husbandry practices such as listed above have served most of us very well over the years, and I expect will continue to do so for many years to come.
Cheers!
. The paper further asserted that the use of antibiotics is an economic necessity in shrimp hatcheries:
