putting "stuff" in the water isnt good......finding out what it is first, would help...a pic certainly will help allot but in the meantime, does it look like small grains of salt or more like an injury of some kind?
if it looks like salt, its probably
ICH and to treat ich you can slowly turn up the temps to 84-84F for 2 weeks....add an extra bubble wand or air stone as warmer water has less oxygen..do 2 gravel vacs a week to clean the ich spores that will fall off the fish, out of the subtrate....make sure the water you put back in the tank, is the warmer temps also..you dont want a temp shock.....good luck!