I have no idea whether that would work. Bentonite, IMO, is meant to be mixed with existing soil and then allowed to expand when wet.

Dealing with powdered bentonite is a real character builder. It is unbelievably slick. If you have any moisture on you like sweat the stuff is almost impossible to wipe off.

I think I would contact someone at a bentonite mining operation and start asking for opinions.

It's not about the fish. It's about the pond. Take care of the pond and the fish will be fine. PB subscriber since before it was in color.

Without a sense of urgency, Nothing ever gets done.

Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley Rancher and Farmer Muleshoe Texas 1892-1985 RIP Grandpa