I have resealed multiple tanks over the years. I have a 135 running that I resealed about 4 years ago. Removed all the old silicone, cleaned with vinegar, buffed with a clothed and resealed. Same with a 55 and several smaller tanks. Never had a leak. Buffing and vinegar are key to removing all the old silicone. If you want a clean line (I used black once) use masking tape.