Water temps DO matter in that axolotls will quickly perish in warm(tropical fish) temps. As for eating the fish, well, depending on the species and size bought would depend if they will eat them. I know for sure that your common pleco will grow to lengths of 18 to 24 inches and are NOT solely vegetarians. Some Cory cats get a decent size(4-6 inches). Both Cory's and Plecos are armoured catfish and some Plecos have poisonous(not deadly) pectoral spines. Bottom line something will die in the tank.
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"I am all that is Divine, I am all that is Evil.
I am the one who brings forth Death,
On the wings of a Weevil." JSKII