I had a tank that cracked years ago. I took it to a glass shop and had a new piece of glass cut. I then took it to a window maker and had it seales professionally with silicone (aquarium grade). It worked for about 4 months and while I was at work one day, the seal broke and blew out the glass. 29 gallons of water all over my apartment and loads of dead fisf.....and the smell....OMG! Try Craigslist and get another tank if you can or search other listings. Losing sleep at night and worrying all day is not worth it....Trust me!!