yeah i was reading about salt all the time, n from what i read it helps to prevent things a little bit but then if they do still catch something then it is harder to get rid of because it is already resistant to the higher level of salt n the reason it works is like you said it changes the osmotic pressure and kills off the organisms, so now i only use salt when treating for something, n thats good about the formalin-3 (im thinking about getting another pictus so now can know what to treat it with if it shows any illnesses during quarantine) im just really paranoid about copper because i may one day use this tank for saltwater, and if a tank has ever had copper meds used in it, you cant EVER put corals or invertebrates into the tank unless you totally redo all the silicon and scrub EVERYTHING, thats how sensitive they are to copper traces in the water!