torn fins on my plec!!!

[El_diablo]

Iv got a 130 litre freshwater tank that's bin up n running for around 15 months now and iv got a plec that's approx 2 years old that we'v had for 8 months or so and all has been fine until yesterday! I notices he had holes and tears on 1 of his small fins that I'd never noticed befor so I tested the water and found no problems at all with the condition of it (no ammonia no nitrite 5-10 nitrate and a ph of 6.5 - 7 and it seams to of been settled at these levels 4 a while now) so I put a dose of fin rot medicine in last nyt. Has anybody else had this sort of problem before and is it fin rot or possibly something else? I do have 4 black widow tetras that r a little nippy but I can't imagine they'd bother with someting much bigger like a plec, would they? His behavior has been pretty normal tho, il try n post some pics.

Anyway thanks for lookin

 

[dkpate]

That looks more like fin rot than nipping. How often do you change part of the water, and how much do you change?

 

[El_diablo]

I do around 15-20% weekly, iv treated it for fin rot and over the last few days it has improved loads so all should b fine now

 

[dkpate]

Yes, you treated, but you need to find out why it happened so it doesn't happen again.
I change 50% of my tanks water every week, maybe you should try doing a little more?