Thanks I was thinking of using ice cubes but thought that may hurt the water readings. Never right of freezing gallon jugs. As long as it doesn't get higher than 82° I should be alright though? Thanks again.I use frozen gallon jugs, my 125 sits in front of a window that gets sun most of the day and even with my house temp at 65 the tank will get up around 85-86 some days. No heater on that tank, only drops to about 78 on cool nights. I usually don't worry about it till the tank is above 82, then I just rotate a gallon of ice every hour or so.