Dry Ice?

[Ryank]

Great Info everyone and thanks, Perhaps in the fish cooler I would use it to keep the other ice blocks frozen longer, and remove when fish goes in. Really good info though, thanks!

[wtenglish]

Not sure about dry ice but I do have experience with Rock Salt. If you sprinkle a small handful it will keep your ice many times longer. Caution, if you add to much it will freeze the cooler solid. If you've ever made homemade ice cream you'll know what I'm talking about.