I used to change it every night and I used to use cold water and crushed up ice. it produced a nice cool bong hit I would crave as night approached.
pro-tip right here
My only criticism of ice in the bongwater is the way it causes condensation inside the chamber. I like to be able to see the smoke as I pull it.... sometimes my lungs aren't the best judges of how much they can inhale without giving up, and with the way the ice cools down the smoke there's a good chance I'm gonna overdo it.
Regardless, though, icy bongwater really does give you some amazing hits.