bdog, I would add ice. We've used both frozen milk jugs, and water bottles. It just depends on the size of the tank.
When we move fish, I tend to stop every few hours and recheck the tanks. We've never had a problem, but I credit that to carrying extra hose, clamps, flowmeters, etc. It seems like nothing fails if it's something I can fix on the side of the road. A backup bubbler might be a good investment.
