Sorry that happened. I'm going to assume you bought a new one on sale to have a good looking sump. You can peel the molding carefully and replace that pane of glass with one off another equal dimension aquarium. I've done that with my finds that I resell. If you don't care what it looks like and I don't know why you would if it's out of sight/out of mind, patch it with scrap panes like others suggested and reseal as needed. It'll get by. I guess the biggest motivation overall is quality versus quantity. You can definitely find an aquarium in a garage sale or on LetGO or craigslist for cheap. I picked up a dirty 75 gallon with a stand, pumps, accessories, and light for $40. She gave me a 10 gallon running with hood, pumps, dino bichir and gouramis as well. I came away with a free 75 gallon with stand that I setup my way on my steam for free.