Aggressive Pleco? Eat or Attack Other Fish? Disappeared

Topic: Do plecos ever eat small fish or are they strictly vegetarian? Mine seem somewhat aggressive towards my other fish at times. Would they ever kill the other fish and eat them? I’ve had a fish disappear and wondered if they ate them. Need help.


*Awarded Answer 
Posted by Chris W: I wouldn’t say that plecos are generally aggressive per say. But I will say that if you have a dead fish in your tank and your plecostomus is hungry… he will be eating it. That’s very common to have fish disappear. Usually a fish dies and sinks to the bottom and then the pleco eats the entire fish. There are lots of different types of pleco catfish so it really depends on which type you have particularly. To stop your pleco from eating other dead fish or sucking on their slime coat, feed them a super good diet. Some of the algae foods are low quality. Get some Omega One Algae discs. Here is a link and picture:

Omega One Veggie Rounds, 4.2 Ounce Container
List Price: $9.29
Price: $9.29
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pleco eat other fish aggressive

If that fish is dead or close to it they will eat or try to eat it. They also like frozen blood worms and brine shrimp.
There are several hundred different species of “Pleco” and they can be pretty much anything from herbivore to carnivore. If fed a proper diet, they typically will not be predatory.
Herbivore! The word I was looking for! It was on the top of my tongue and couldn’t think of it! Hahahahaha
A lot of pleco species are actually carnivores. My common killed my Oscar over a beef heart once and my gold spot rhino eats live ghost shrimp.
Dead fish yes and I believe they’ll eat most fish if they can.
Well…… that’s not good.

Our pleco lived with 9″ Oscars in our downstairs tank.  We want to redo that tank so brought the pleco to the 75.  I have had one platy disappear… hes a biiiig boy so I was hoping he was going to be safe…. now I’m not so sure.

they won’t eat adult platies unless they are already dead. They aren’t predatory in the sense that they hunt larger fish, but if something bite size wanders in that’s a different story.
So that’s probably why i keep counting 5 cherry bards and i had 6 i swear i can’t find the other one . Common pleco probably eat him.
Plecos have a super complex diet. To be 100% healthy your pleco should eat drift wood, algae, biofilm, dead fish, fruits and plants.
There is no single diet for all plecos. There is also no evidence to support any pleco outside of the Panaque and Panaqulos genus’ to require driftwood in their diet. And plecos don’t need to eat dead fish to be healthy, that’s completely silly. Plenty of other ways to give them protein.
well I was going off of what they would eat in the wild. Not being “silly” just being straight up. People buy plecos thinking they just eat algae. When in reality they require much more. So protein such as fish is natural for them.
Yes. Plecos need a varied diet and shouldn’t be relied upon to survive off of algae and leftovers.  How much variation depends on the pleco.  Plecos like those in the pseudacanthicus and Leporacanthicus genus’ are primarily carnivores. My L114 and L091 won’t touch veggies at all.  Other plecos are more herbivore leaning. There aren’t any that I know of that are 100% herbivore.
and that’s what I was trying to say. I wasn’t aware how ever that only a few plecos eat wood I always have drift wood in any tank with a pleco.
I think driftwood is a good thing to have for any pleco because it’ll grow biofilm, and algae and such but as far as actually eating as part of their dietary requirements that is strictly the Panaque and Panaqulos.
Seen them in your LFS? They feed off the dead tankmates lol especially when they’re little.
My pleco will hitch a ride on my goldfish when they’re being mean to him and try to steal his algae wafers lol
Actually plecos love the slime coat of goldfish. He’s trying to suck the slime coat off which will kill.
I’ve heard bristle nose can chase and suck the slime coat off a fish and kill it but I’ve never had an aggressive pleco… I’m not much help…
They will be grateful for the extra protein from a dead fish but they won’t ever kill one best guess your water parameters are off or you have another fish doing the killing.
if parameters are wrong why 1 fish every week ? and why not ghost fish is not getting issue.
they are found dead. 

it swimming fine few hours back liek 4 or 5 then  i saw pleco all over it.

Plecos arent killers but have been heard to suck on other fish. Damaging them. Rare tho see itmore in SAE.
No offence intended but I would rehome the fish or put more research in as it doesn’t look like you have been given any advice on the fish until this point.
I had a bristlenose eat a Cory before. I always thought it was another fish until the bristle nose died with a Cory half out of its mouth. Never lost another fish after that.
My plecos will eat dead fish. Never had them kill. My bristlenose chases things away from her algae wafers and zucchini slices. But then goes back to chowing on them.
Plecs and Knifefish can kill fish very easily, although most common types of Knifefish typically kill to eat whole rather than kill prey it can’t or won’t eat. Even the territorial Ghost Knifefish rarely kill conspecifics so suddenly. 

Many species of Plecs, especially toothless can chase down fish to feed on their slimecoat, but it isn’t that common. Unless the Plec is fairly large, it wouldn’t be a sudden kill either.

It probably just died, these things do happen unfortunately, and the Plec came to feed on it. 

Telltale sights are white patches on the fish usually mean plec slimecoat feeding, and missing tankmates would be from the knifeifsh.

Yeah common plecos can be a pain depending on which species it actually was. There are like six different ‘common plecos’ at this point. I’ve never seen one go straight predatory though outside of sucking on goldfish and bichir. Shame that happened.
Yeah I avoid common plecos for those very reasons. Look at the hypancistrus family if you want some more tankmate friendly species, and frankly far more stunning, that wouldn’t ever provide such an issue. Mainly carnivorous genus though.
He is currently giant and happy living in a huge indoor pond with turtles.i have 4 kids and gone 90 percent of the week……im out of the hobby for now.
Even to find an adult killer common pleco is extremely uncommon. They will absolutely attach to sick fish and suck off slime coats. They’ll go after sting rays because they sit on the bottom, and I’ve seen them try and attach to discus to get slime coat as well, but they are not carnivores. They are obligate omnivores…not predators.
Common plecos when they are bigger are meat eaters it is not uncommon at all for them to kill, they need a meat based diet for proper digestion,health and growth.
I repeat….they are obligate omnivores not predators.

Yes some will kill, they can become aggressive and territorial in improper environments. A common pleco (any of the many species) will choose a dead piece of shrimp or zucchini over a live fish any day of the week.

I’m done with this conversation. Enjoy your day.

Many moons ago I did have a good size Black Ghost, loved that guy, but I never found him to be too aggressive to my other fish, never killed any that I know of or remember.  Do agree that in the OP’s pic pleco is getting a free easy meal and cleaning up.  I seldom find my missing fish, my background is black so I always tell people I have a black hole in my tank as I rarely find any bodies if I occasionally lose someone and everyone usually agrees the pleco is cleaning up. LOL