Agree with with the above suggestions, however it really depends on the strain of ich. I recently encountered a strain that was extremely difficult to kill. I ended up keeping the tank at 86.5F for over two weeks until it finally succomed to the high temp(s). Fortunately, most strains of ich don't handle temps over 82-84. Regardless, it's important that you maintain the increased temp an additional 7-10 days after ALL white spots dissapear.