I raise to 85 degrees..fish handle it fine.. It causes the life cycle of the ich to decrease causes white spots to fall off faster..that when medicine can kill it..even if no white spots does not mean they healed..they could still have spots inside there gills..i always treat for 2 weeks to make sure it good..good news if fish survive u treatment..they build strong immune to it and it harder for that fish to get it again..i had ich years ago as a beginner and had a bala shark he got ich treated with kordon..in next 4 months ich hit the tank again cause my lack of quarantine new fish..he never got white shots the next 2 outbreak s..good luck