Ice packs to chill tank in summer?

[GoFish]

Or that, same idea as above but ziploc freezer bags won't burst

[Aquattro]

Probably a calculation somewhere, but would include water temp, ice temp, air temp, surface areas of those parameters. Not something you work out in your head. Trial and error, unfortunately.

[lastlight]

i threw in about 10 water bottles (didn't drain any water and they never burst in my freezer). took about 2F off my tank temp and quite fast too. took about 10 min for ~ 130 gallons. too fast for my liking and my hot main floor (29C) raised the temp back up in less than an hour. a fan on the display is a better idea i was just too lazy to set one up.