I was going to try this ghetto mans chiller this year. Since everyone's family hate the heat output from the chiller. I thought I'd get a long water change hose and coil it up in a cooler. Fill it with ice and a little water for contact. Then run a pump from the sump and either return to the tank or back into the sump. I've left ice in a cooler for 3-4 days without it co.pletely melting. I'm certain it'll work. Maybe set up a temp controller so your tank doesn't freeze.
I got one of those Air King fans like BRS sells... with only 1 of them setup, it's keeping my tank at 78 - 79 (tank is 125 gallons). Without it, my tank was getting to 83 or so (I have no central AC and and the house gets pretty warm). It does require a lot more top off... about 2 gallons a day vs 1 gallon.
This is why I put my tank right under the AC vent, my tank doesn't go over 78 in the summer. I would definitely be investing into a chiller If I didn't have AC or the tank was not holding acceptable temps. It would be worth the money up front when we get into august and frozen water bottles don't work.
with this dry heat we are getting evaporation cooling is great but you have to watch your salinity if you dont have a ato. when it gets humid evap cooling doesnt works that well. thats when i my fish room ac kicks in and cool the tank.
I tried the coiled tubing in an ice chest method once, years ago, and all the ice melted in 24 hours. Not very practical IMO. One thing I've always wanted to try though just for the hell of it is to pick up a used mini fridge for cheap and modify it into a chiller. A controller would still have to be incorporated though, and with my current tank, I've never had overheating issues so I've never bothered to try this.
How well did it work? And was your cooler completely closed? I was thinking 2 bulk heads. One in one out. I'll probably never end up trying it since I plan on plumbing everything all the way out the back yard. So chiller heat won't be an issue.