Straignt NaCl you buy at farm stores- "stock salt"-no additives or anything else to worry about but treating the entire pond is something I will never speculate on because it never goes away and I don't know that this has been used by any of the bio's I work with. I'll defer to someone with actual experience in that.
The only thing I CAN add is be very careful if you have or intend to have any catfish as the salt will burn/kill them if concentration is too high

Last edited by Snipe; 10/11/20 10:14 PM.