I strongly suggest you don't go there to buy stock - a dead fish left in a tank is a sign of extreme neglect, and the fact that the pleco was trying to eat him is an indication the poor creature was probably half starved. I know some idiots think that you don't need to feed plecos - they can just live off the molecules in the water or something (since there's no algae for them to eat).
You should report them to the RSPCA/SPCA/whatever other animal welfare organisation you know.
actually if I remember right there are some pelcos that are carnivioris and on a lighter note when my pirhanas were babies my pelco terry would clean up after them by eating the heads of the neons that they ate
My plecs are anything but vegetarians, give them the choice between a slice of courgette/cucumber or a dead fish/mussel/cockle theyll take the meat option everytime. Feeding meaty foods to plecs is good for them and helps them to grow quicker and remain healthier.
a friend of mine has a huge Pleco that eats frozen mosquito larvy. It doesn't wait for it to sink to the bottom either. It turns upside down and eats from the surface . His tank mate, an oscar (equally large) doesn't like him doing this.
That's part of any catfish's nature, to clean up dead stuff. Gross, I know; but, in nature there has to be a clean up crew or we'd be in a nastier world than we already have. (Thanks to human intervention. If we leave the animals to do their job, things would be a lot cleaner.)
Sorry, in my environmentalist mode today.
Save the whales. Clean up the world. Don't litter. etc.