Repairing aquariums

Question
QUESTION: I was wondering if there is anyway to safely repair a crack in an aquarium so that it will hold water and not leak or crack further?

ANSWER: Debbie,
Seals can be replaced with Aquarium sealant if its just a seal. But cracks... it depends on the size and the area cracked. Panes can be replaced in aquariums when necessary. Your local glass shop should be able to get you the size and thickness you need. But unless its a large tank it may be more cost effective to buy a new tank. Without knowing where the crack is and how big it is thats about the best answer I can give you. Your local fish store probably knows someone that can even do the glass replacement for you rather cheaply. Hope this helps.

~Glenn

---------- FOLLOW-UP ----------

QUESTION: It is about 3 inches according to the current owner and it is on one of 72 inch sides, I believe.

Answer
Debbie,
Ouch. Thats a pretty bad crack. 72 inches... this is a large tank too. 125, 150 or 180 gallons at least, right? The only way to safely get that aquarium holding water, is to replace the cracked pane. Judging by your comment "current owner" its one you're buying or being given. If it's a real steal then replacing the glass pane is an option, could cost between $90 and $150. If not, then new may be the way for you to go. Most aquariums at that size(125gallons) are around $325 to $350 brand new. Trying to repair the crack just isnt safe. Injection/pressurized repairs are not going to withstand the water pressure and have toxic additives that will leach into the aquarium. One other option(not a very aesthetically pleasing one) is to use aquarium adhesive, and aquarium sealant to adhere a piece of marine treated plywood to the cracked glass pane and make the cracked side the back of your tank. You can even paint the plywood with a marine grade paint first for a colored backing. The crack would have to be filled with aquarium sealant first. Make sure the sealant does not differ, higher or lower, from the surface of the rest of the glass pane. Then completely adhere the plywood to the cracked pane and clamp in place till dry(and watch that the clamps arent too tight or you will add to the cracking). You will always see the crack, though this would make the aquarium usable without the expense of new glass being installed. Wish there was another option  but thats about it. Hope this helps.

~Glenn