Pleco Aggressors?

[saradora]

I have a 29 gallon tank with what I think is either a queen arabesque or an L-333, a common pleco, a clown pleco, a black ghost knife fish, and (formerly) three dwarf gouramis. One of the gouramis suddenly developed a massive hole in its head, directly to the side of its eye. My question is whether my L-333 or whatever it might be could be capable of this. I was reading in the Aqualog Most Beautiful L-Numbers about the different kind of mouths that plecos have, and this fish has the mouth with the most bite capability. The common pleco and the black ghost develop tears in their fins fairly often, and then the gourami got the head wound. The L-333 and the clown pleco are the only ones with perfect fins and tails--they just glow with robust good health. The L-333, the common pleco, and the black ghost are all the same size (about 4"). The clown is tiny, barely even 2". I don't think that the L-333 eats anything but driftwood and meat--I have never observed it eating anything but bloodworms and carnivore wafers. The clown eats a balanced mixture of both (and does not have the same kind of mouth as the L-333). Any thoughts on what caused my gourami's fatal head wound and the other fishes' fin tears?

[dazza]

I would look to your knife fish as the most likely cause, although the black knife fish is the least aggressive of the species they still go for other fish if they don't have enough living space - they are also ravenous eaters of bloodworms, krill, brineshrimp etc...

my pair grew from 2" to 6" in 3 months before i removed them to a new home

Dazza