Block ice is used to slow the temperature drop rate. Cube ice has such a large surface area that it can kill the fish. The temp can drop so fast with cubed ice, the fish have no time to acclimate. A little dechlorinator is always a good idea with ice, regardless of the water source.
That's interesting Rex. I have dumped in the bag ice from gas station/convenience stores for years and never had a problem. All the ice producers I know remove the chlorine/chloromine before making the ice. They have special filters that also make it as clear as possible.
According to the literature I have about adding municipal water to recirculating systems that had chlorine in it, as long as it is 10 percent or less of the volume of the system it's not a problem.
Cecil, all my concerns and experience is in hauling the fish, which is stressful on them....ANY chlorine or an overly fast change in temps are causes extra stress and increases chances of mortality, be it in an hour, or a week after the stress. I use bag ice also when I must, and I expect problems when I do. I have to make decisions on which stress is more deadly, Higher water temps with lower dissolved oxygen (and higher O2 flow to compensate) on a long haul, or a more rapid temp drop that slows metabolism for lower O2 demand along with increases in dissolved oxygen availability. I also do not have the time or desire to test for chlorine levels, incase a "filter" was malfunctioning, so I treat (my dechlorinator {Prime} also binds free ammonia).
