I have this weird drip mark on outside of glass I cant get off. I tried vinegar for a few hours and it still sticks. I was able to scrub some off with a sponge but it scratched the tank so I stopped. I've tried a scraper with vinegar too but it also starts to scratch the tank. Idk what it is. Water drips just whip off. Not sure what this could be besides all, calcium, or magnesium from manual dosing.
Any ideas out there?
Any ideas out there?