What happened to my rainbow

[Apocalypse_Gold]

Saturday I purchased a praecox rainbow. This morning it seemed perfectly healthy and was eating fine, interacting with the other fish (maybe being a bit of a bully), and now he is nearly dead, laying on his side. My ammonia is at 0.0, ph is 6.9, low hardness, water temp 72. I had been feeding jungle pepso food because I had a guppy I bought at the same time die from an intestinal worm. I had also put in some melafix. There are no external signs of disease. Any ideas of what could have happened?

[TankGirl]

First thing to do is quarrantine that fish. Second, what are your nitrite and nitrate levels? Any other changes (gravel vac's, filter cleaning, etc.) recently?

In the absence of any obvious water quality issues you are left with a few possible causes. One is that this was a fish with poor breeding and had some kind of illness or defect before you brought him home (was the fish quarrantined before being put into the tank with your other fish?). The other thing might be acclimation. If he went from a tank at the breeder with thus-and-so pH/nitrate/temp, then went to the LFS with different values, then went to your tank with a third combination of values, this could stress the fish to the point of illness. If you slowly acclimated him to your water before actually freeing him into the tank, then my guess is he was ill from the start, and possibly should be returned to the LFS.

Sorry about this - I keep rainbows and they are fabulous fish, hope he makes it through.

[Apocalypse_Gold]

He already went to that fish tank in the sky . My nitrite is at 0. The other fish in the tank were purchased in the same time. This is my qt and I had just moved the fish that were in it to my main tank. I retested my ph and it's more like 7.3, which some sites I visited said was ok, others said that's too high. Are there any warning signs that a fish is having trouble adjusting? This guy appeared fine until he was doing the backstroke. Any extra advice for keeping rainbows? This was my first one.

[Apocalypse_Gold]

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!