Hey man the exact thing happened to me. My BGK fell asleep behind my heater and got burned.. I grew him 3-8in in 6 months. He died the day after the burn. If yours is still alive, you got a chance but a slim one. I would get some melafix, and add some salt. Take it from an experienced BGK owner, the melafix is somewhat an old wives tale, but I have noticed faster recovery with it then without, and the salt will not hurt your BGK, 1 teaspoon per 10gal should be fine, your not treating for ICH here but the extra electrolytes will reduce the stress of your fish. If it starts looking worse, some pictures would help us identify if it proceeded to a bacterial or fungal infection - if you go to treat for this DO HALF DOSES. Your fish is already stressed and a knife-fish. I would do daily water changes as well. And your knife is moving way too fast and all the time for the pleco to have done this, unless m a y b e it was a really small tank and a large pleco, but I doubt it. I moved my heater and put it horizontally and on the bottom, and haven't had a problem since.