Tannins effects on fish, specific acids

I'm known to crotchety about some things such as adding almond leaves to cure aliments, breed fish and what not.
I want to know why and what about the leaves allows to to occur, not just some guy who thinks it might work and then the bandwagon starts and everyone starts adding garlic or aloe to their tanks for no good reason.

So poking around to see if there is any credence to such speculation is a wise idea. Specifically, if we can figure out what chemical compounds are effective, then this knowledge can be applied to a wider variety of leaves, products and tonics.

The article below is a good example or what compounds are important as well as parameters. It also discussed what rate of removal such compounds had in a simulated pond etc.




"North American Journal of Aquaculture 1999;61:304–309

Effects of Selected Water Quality Variables on the Persistence of Tannic Acid and Related Compounds under Simulated Aquaculture Conditions
Guojing Zhao, Ahmadu A. Jaiteh, Wenxian Wang, and S. Edward Stevens, Jr.

Department of Microbiology and Molecular Cell Sciences, The University of Memphis, Memphis, Tennessee 38152, USA

Abstract.—Tannins have potential commercial applications in aquaculture for the prevention of piscine diseases and off-flavor in fish. Selected water quality variables, such as temperature, pH, dissolved oxygen, light intensity, total hardness and total alkalinity, and available nutrients found in fish ponds were examined for their influence on the fate of gallic acid, methyl gallate, propyl gallate, and tannic acid. It was determined that total hardness and alkalinity were the most effective factors in the dissipation of tannin compounds. High levels of selected water quality variables were significantly different from low levels in their ability to transform tannin compounds. It was also found that natural suspended solids were effective in precipitating 60% of the methyl gallate and 81.3% of the propyl gallate per week from solution. Abiotic processes, such as physical transportation and chemical transformation, affected the fate of tannin compounds in a simulated fish pond. This study may guide the use of tannins as a feed additive or disease treatment in the management of fish-farming problems."

 

Tannins tend to be pretty toxic in general, something many don't seem to realize.
When bacteria break organic matter down, it quickly changes and once bengin compounds are now toxic. But over time, most things are decomposed effectively.

The key is into what and are those things able to help fish/plants(generally not) and if so, how long do they presist?

Regards,
Tom Barr