Plecos' close scrape?

[Oddball]

Hi all, got a bit of a problem with a common pleco. I saw him ywsterday and he appears to have lost a large amount of colouration and a few of the plates on his tail, giving it and odd skeletal appearance. Of course my first reaction was to watch him for distress, and he seemed to be acting fine, and he fed well. I've started a course of Melafix. but im still a little worried on what caused this. The tank is a Lake Malawi setup (so alkaline etc etc.) and is coral gravel with plenty of rocks, im wondering whether this scratched/caught his tail. The other thing may be the juvenile Polypterus weeksii added two weeks ago, but it seems too STUPID to attack a pleco and has enough difficulty finding lance fish in the tank..............sigh. So what do u thinks wrong with plaeccy and what should i do with him?

 

[My Head Hurts]

Ahhhh, poor pleccy, hes such a cool thing. Apart from treat him i wouldn't really say there's much you can do, I wouldn't worry about it, and from what ive seen of your poly it wouldn't attack anything that didn't live about an inch under the gravel....