I am also ready for this great DIY project that will come out of a very common problem that everybody worries about each summer.
well i just dont want to worry about it. i freeze them let them thaw out in the tanks some times there is some leaks this way it doesnt matter it the water gets dumped in.You freeze tank water in the bottles? If it's sealed in the bottle, wouldn't normal tap water be okay?
How do your fish react to the icebergs?
I was just thinking on the lines of those party ice cubes. You know the little ones that look like minature golf balls and such. Just plop a few of them in and rotate as needed.