Pleco Torn Fins

[Shawnoceanside]

I've had my pleco for about two years now and for the first time, he got himself jammed up in a decoration. He ended up tearing up his dorsal fine pretty badly. There's a couple little holes and two small tears on it. I went to the store and got some Melafix for him, thouogh it says to remove your carbon if possible. In my filter, the only cartridge I have is a carbon cartridge. Wouldn't it be dangerous for all the fish to remove that cartridge? Also, it doesn't say how long to keep it removed. The filter is a Cascade 300. Any help would be appreciated!