I have heard many things on this topic as well. However through personal experience as long as you keep fresh water and some type of fish saver "rejuvinaide" or whatever you should be fine. My livewells are aluminum, but they are gravity fed with an aerator, so there is plenty of fresh oxygenated water rolling through. During a tourny, I usually keep 1liter frozen water bottles in case I get a fish that is stressing. It seems to help but you don't want to over do it with the cooler water. I usually only do that in july and august, the hotter months here in indy.