88 is pretty high for anything to be living in for more than a day or two. One of my 20 gallons usually runs around 82-84 all summer long and I've had no problems so far. Any higher than that and I'm dumping ice cubes into the tank.
I run my tank at 80 which seems to be pretty high compared to other's on this site (I think). I used to get Ick probems now and then, never seen it since. The main reason is my heater sucks and won't stay constant except at this temp (when set to 65 lol) or higher. New heater in my future.