Who Gives A Fish Forums

My pleco has been acting super aggressive lately, chasing my other fish and even nipping at them. It's a 55 gallon tank with plenty of hiding spots, but he's still being a bully. Anyone else dealt with this?

Yep, plecos can get territorial, especially if they're older or if the tank's crowded. What's your water change routine? Sometimes poor water quality can stress them out and make 'em act up.

I've got a similar issue with my common pleco. He's in a 75 gallon with driftwood and caves, but he's still a jerk to my cichlids. Gonna try rearranging the decor to shake things up.

BoldRom wrote: ↑Sun Jun 22, 2025 4:17 pm Yep, plecos can get territorial, especially if they're older or if the tank's crowded. What's your water change routine? Sometimes poor water quality can stress them out and make 'em act up.

Agreed. Also, check if he's getting enough food. Hungry plecos can get feisty.

Mine chilled out after I added more algae wafers. Maybe yours is just hangry? How often do you feed him?

Plecos are weird like that. Mine's cool with everyone except my angelfish, which he hates for some reason. Tank's a 40 breeder with sand and driftwood. No clue why he's got a vendetta.

Aggression can also be a sign of spawning behavior. Is your pleco male? Males can get super protective of their territory when they're ready to breed. Might explain the sudden change.

Or maybe your pleco's just a jerk. Some fish are like that. Mine's a total diva, but he's got personality, I'll give him that.

Florionix wrote: ↑Sun Jun 22, 2025 6:59 pm Aggression can also be a sign of spawning behavior. Is your pleco male? Males can get super protective of their territory when they're ready to breed. Might explain the sudden change.

That's a good point. OP, how old is your pleco? Males usually show more aggression as they mature.

Mine's a chill dude, but he's got his own cave and I feed him zucchini twice a week. Maybe try diversifying his diet? Could be a food thing.