Since Beta Glucan is scientifically proven to enhance immune response and is obviously safe (even recommended) for human consumption, why would it not be safe for my fish to help enhance their immune systems? People toss in garlic and ginger, but there is no scientifically proven benefits thus far to these methods.
The problem is that Beta-glucans do not enhance the immune system, instead it
stimulates the immune system. In layman' terms that means that the immune system is always "on". While this can be helpful for short term, it is detrimental in the long run.
Some of your most troublesome human diseases are those that are auto-immune diseases (i.e. over-active immune system) for example Lupus, Multiple sclerosis, Myasthenia Gravis, Guillain-Barre Syndrome. While I am NOT implying that Beta glucan will lead to these diseases, they are the result of improper stimulation of the immune system.
Even more interesting is the article "Candida albicans Derived Fungal PAMPS, CAWS, Water Soluble Mannoproteinâ€"œB-Glucan Complex Shows Similar Immunotoxicological
Activity with Bacterial Endotoxin from Escherichia coliO9" Biol Pharm Bull. 2006 Feb;29(2):240-6 (which comes from a scientific peer-reviewed journal) which states that CAWS (B-glucan extracted from C. albicans) has "has various biological effects, such as anaphylactoid shock and coronary arteritis."
The authors demonstrated that B-glucan had similar mortality rates as does E. coli LPS...Hmmmm mortality....anaphylactic shock....both bad things.
Unfortunately, every site that I looked at concerning B-glucan (including betaglucan.org, which is sponsored by Nutritional Scientific Corporation, a company that sells B-glucan...hmmmm...) are NOT scientific sites. They are disseminating scientifically unsound conclusions based upon misinterpretations of published data. In addition, much of their "data" comes not from peer-reviewed journals, but from other dubious sources.
My point, as a microbiologist, is at best B-glucan would be a waste of money to add to the tank, and at worst could have long-term detrimental effects on your livestock's health.