Aggresive Pleco

[NekoOo]

My pleco, who I have named Aries due to his sudden aggression, has started to show a territorial nature towards my goldfish. They have lived together peacefully for the last few months and the pleco never showed any aggression, even when the goldfish would hang out around his little castle/cave. About a week or two ago I replaced the castle with a big piece of driftwood. Since then my pleco has happily made himself at home in the darkness the dw supplies, but now when the goldfish try and go near his cave he attacks and chases them around the tank. He guards his little cave all the time and I have also noticed that he is overall more active, even in the day. I think he's taking charge of my tank and showing those veracious goldfish who's boss...FINALLY. I plan on separating them very soon but I was just wondering if anyone had any ideas as to why he suddenly began to act this way? Just curious as to why the sudden change in his docile nature.

Also my pleco is only 2 or 3 inches long and yes I am aware that they get aggressive, but I thought that usually happens when they get much larger?

 

[RussellC]

The pleco sounds like it is simply establishing its territory.

Glad to hear you are planning on separating them. Even if the pleco weren't acting aggressive, they are known to suck the slime coats off of goldfish and prefer warmer water than goldfish do.

Best!

 

[Cynic]

As above. As your pleco gets larger it will become more territorial. Unfortunately goldfish tend to be sitting ducks due to their size, colour and docile nature.

My pleco when young used to get shoulder charged by my bristlenose pleco, he has recently started returning the favour now he is getting large.

 

[bettaowner]

As plecos age, mainly the males will become territorial.