Is it definitely torn, and not fin rot??
Again I would use tights
Secure some around the inlets also. it means that larger bits won't get sucked in but should not create a huge problem if you are doing weekly water changes. I covered a filter completely using a pop sock in a fry tank, to stop the fry getting sucked in. Only thing is, after a few weeks there was a fair bit of algae on it, but you can just replace it
thank you again, yeah im 99% sure its the filter, tail was fine one min went out came home and it was a mess, i thought he may have been tail biting, so started using melafix but not getting any better, then today looked in on him and he was sat with his tail in there
so popped a bit of food in to move him, and it was worse again. I will use the pop sock as you said but is there anything different i could treat him with or should i just do a water change and carry on as i am.