Cooling Tank Water During The Summer

[rdebonis]

I have 3 tanks of Long Finned White Cloud Mountain minnows and the temperature in the tanks gets as high as 84 F during the summer. These fish prefer temperatures between 65F and 74F. I know I am stressing them but there doesn't appear to be any problem with them because they are active and eating........ However, I can't get them to breed at these high temperatures. The tanks are 1-30 gallon and 1-20 gallon.

Does anyone have any suggestions other than a chiller. I do have air conditioning in the room, but I keep the tank lights on 10 to 12 hours per day for the plants and the tank temperatures get rather high. I was thinking of reversing the daylight hours by putting the lights on in these tanks from 10PM to 10 AM, but I am not sure if it will affect the fish.