When I was a kid, I talked my parents into getting some of those little, itty bitty turtles that pet stores sell. I don't know what it is, but I swear this breed of turtle has a death wish. We would bring one home and the next day he would be dead in his little turtle tank, so we would return to the pet store for yet another speciman of turtalis mortis tomorreus. We must have gone through 4 turtles before we gave up for fear of eventually wiping out the species.
We never did know what caused the problems. We followed the instructions that came with the turtles carefully, we even consulted a vet, but every turtle isisted on shuffling off this mortal coil almost immediately upon arrival in our household. So we switched to hamsters. They seemed to have a stronger will to live.