Aggressive Bristlenose killing Corys?

**Brhino** · 10-25-2010, 07:46 PM

(mods - not sure if this should go in pleco forum or cory forum, so I compromised and went with general forum. Move if needed)

I've had bad luck with Corys. 5 of 9 dead, with one of the four survivors looking very unhealthy. Deaths have been pretty inexplicable, often coming completely without warning, and the timing has been spaced across several months that I've had them.

I also have a bristlenose pleco in the tank, and lately he has been getting more aggressive towards the corys. He will occasionally chase them, either away from food he is eating or wants, or away from the cave he has dug for himself under the driftwood. The chase is always brief and I have yet to see an actual "attack" (not sure how a pleco would attack exactly anyhow, as they don't have predatory mouths), but I'm starting to wonder if the deaths and the aggression are related.

possibilities I'm considering:
1. The pleco is chasing the corys, which is causing stress, which is contributing to their deaths.
2. The pleco is actually killing the corys, when I'm not watching.
3. It's just a bit of harmless chasing, and the deaths are unrelated.

points to consider:
1. The aggressiveness is a pretty recent development. At least some of the cory deaths happened before it started.
2. The tank has lots of hiding spots and line-of-sight breaks, but the corys like to spend 75% of their time in one particular spot, in the open in one of the front corners of the tank. The pleco roams all over the tank. Seems like if the corys were stressed by the pleco, they'd be in more of a hiding spot?
3. There are only 4 corys currently, and I expect there may soon be only 3. I could get more. Maybe that would make them less stressed and less prone to death. Or, maybe it would just give the pleco more targets to stress/kill.

Thoughts?

**Excellence** · 10-25-2010, 08:32 PM

If there's a word that best describes Bristlenoses, they are surly fish.

There's a youtube clip that shows one chasing a pack of piranhas because one took his wood he was munching on. He put them to flight!

**Cliff** · 10-25-2010, 08:49 PM

It could be your pleco. Try lowering (or turning off) your lights and watch them for a while.

Some plecos are just mean ******* !. The largest pleco that I have in my tank is very aggressive. Its to the point when I feed veggies, I have to put 5 pcs in the tank as he will claim at least two for himself and is extremely agressive to the other two plecos AND the apple snail & severums if they get close to what he has claimed for himself.

I'm actually considering finding a new home for him were he can be the only pleco in the tank. But for now, the extra veggies in the tank is working.

**BiGBlak** · 10-25-2010, 09:28 PM

Wow something for me to look out for because im planning on adding 3 corys to my two and weeks later introducing a BN pleco.

**Gisela** · 10-25-2010, 09:38 PM

I have no problem with my plecos towards any tankmates incl. big boy Nemo (common - 16 in). I guess I am just lucky with mine.

**Pleco380** · 10-26-2010, 12:29 AM

I've also seen a common pleco chase a piranha on youtube because it stole a chunk of meat. No one bothers my clown plecos but they don't hurt fish either.

**FinalJenemba** · 10-26-2010, 02:37 AM

I have to ask. I hear talk of pleco aggressiveness all the time, but if they actually to catch a fish they where chasing, what would they, you know, do? Ar they capable of actually doing any damage with that mouth? I mean I know that can suck the slime coat off of discus and what not, but can they actually bite?

**Brhino** · 10-26-2010, 03:08 AM

yeah, that's what I'm wondering too.

**Lab_Rat** · 10-26-2010, 03:17 AM

My BNs hold their own with both my African and my American cichlids. My cories in my 29g were picked off one by one, but I blamed my rams. I've not seen my BN in that tank be aggressive at all.