Lima shovelnose aggression?

[biomechmonster]

We have a 3-year-old lima shovelnose (Sorubim lima) in a 180-gallon. It's full grown (12") and very healthy with a hearty appetite. It gets along well with everyone in the tank except our 16" P. gibbiceps pleco.

Since both fish were put in the tank at the same time, it isn't an issue of territory.

Other tankmates include a 4" lima shovelnose (which the big one hangs out with), an adult oscar, a sub-adult Texas cichlid, two sub-adult bichirs, and four other catfish (including a spotted raphael that more or less spends her whole life in a ceramic cave, two smaller plecos and a 15 year old, 13" P. pardalis).

The two larger plecos like to take occasional swims around the tank, especially the gibby. But for some reason, about half the time the gibby swims around, the larger lima shovelnose follows him, occasionally nipping at his tail. It almost seems playful but I'm sure it's not. But the lima leaves the other large pleco alone.

Water parameters are normal and everyone is healthy.

The gibby is the "boss pleco" of the tank and the lima is probably the most aggressive eater.

Any insight is appreciated!! I'm not concerned about this behavior because no one ever gets hurt or close to it, but I *am* very curious!!!

[PlecoCrazy]

I used to have a large Lima that was fine with everything in the tank except the three striped rapael catfish. Everytime he saw one he would try to tag them. I have noticed that he would also get very upset when there was a fish causing to much commotion by him. He would go after them till they left his area. Over the years I have found the Lima's to be very variable as far as how aggresive they are but I does seem that the older they get the more aggesive they get.

[lima_man]

I have both a gibby and two limas in my tank, and I would say the boss is def the gibby . My limas are 10" and 15" but my 14" gibby is the guvnor. he owns the bogwood.