Last night I was looking at my dead rainbow and in the bottom of the cup I iced him in there was another intestinal worm.

The "big freeze" hadn't killed 'em and it wriggled out after the fish was dead. I think I'll return him (the fish, not the worm) and not buy from that store for a while. This has been a problem at other
lfs I have purchased from recently. I really hate worms.
Update: The store said they wouldn't give me a refund unless I brought in a water sample. I'm going to have another
lfs test the water first and then when they try to say "it's your water quality, not the fact that our fish are being eaten from the inside out due to our neglect, that killed your fish," I can show them the other results and tell them they've lost a customer. I've tested everything. The only thing that isn't at 0 is the pH, and that is about 7.3. I got a second opinion from another
lfs, and they said their rainbows are fine at 8.2!