I just picked up 2 20 gallon tanks (got a good deal on them too! ). One of them had a heater in it and it was working, in water, when I went to look at the tanks. It had a LOT of hard water deposits on it that I scraped off when I got home. But I noticed that it had moisture inside the glass of the heater. That isn't safe, right? I'm thinking that I should just scrap the heater and get a new one.