BRISTLE NOSE PLECO(SUCKER FISH)

 

I have only seen Pleco's eating already dead fish. It may be that your fish died during the night and your Pleco got to work on it....easy meal, its what Pleco's do. Pleco's are generally peaceable fish and a valuable asset to your tank.

Also I agree with the pet shop you should get some algae wafers or catfish pellets (thats what mine like) as Pleco's can't live on algae alone. They are such efficient cleaners that there will usually be very little in the way of algae for them to eat therefore will need supplementing. Pleco's also enjoy cucumber or lettuce :-)

It's because there's nothing in the tank for him to eat. #1 cause of death for these guys is starvation. I'd suggest getting him some veggies, algae wafers and driftwood. Keeping them well-fed will keep them from being aggressive and looking for strange things to feed on. My guess about the fish is that it could have already been dead.

He is hungry. If you clean the tank and there is no algae to eat he will eat what he can. Try some algae discs. You can buy them where they sell the fish food.
Stop cleaning the tank...that is the job for the pleco.
And if the fish was already dead he would eat it also so there is no telling if he actually killed it.

if your new pleco is going after live fish i strongly advise taking him back. if you dont your just gonna have bigger problems down the road.

your pleco was going after the slime coat on your other fish, once they taste slime coat they continue to go after it. there is no way to prevent him from doing it. as plecos become older the become more dependent on a veggie diet and also some meat.
your best bet is to take him back and get a smaller type of pleco.

Plecos are omnivours that's why they ate on your fish. They are not really needed in the aquarium. You have one too many anyway they are hungry.