Cracked tank, help!

Recently bought what I thought was a great deal for an extra enclosure/backup. But when I got it home I realized there was a small crack in the corner. What kind of caulk or sealant can I use to fix it up? It doesn’t need to hold water, I just want something that will prevent it from cracking more, and to cover any potential edges.

Use the silicone sealant specifically sold for aquarium repairs. Don't apply it too thick, as it will dry on the outside & take forever to dry on the inside, & you cannot
use the item until there is no longer any off-gassing...only then it's safe & inert. The smell is acidic as it's drying, more irritating than dangerous, but definitely not
for any pets to be inhaling. It's non-toxic when dry.

Can you feel the crack on the inside (animal side) or outside?

I have used a glass bonding agent to fill an hold cracks, Lowe's has 50 or 60 of them.
As for silicone, if you watch youtube about building wood 150 gallon + aquarium, use clear 100% silicone with out additives. Lowe's an Home Depo have it cheap.

I buy large leakers all the time for $5 or free pick up. I have glued plex over bottom glass, flex sealed a few an other "fix's" to hold the glass (hot glue gun:O). You just need the glass smooth (animal safety) an solid. Now, don't put 10 pounds on rocks in it an a 10 pound turtle.


Want to have fun? Cut the silicone out an take the tank apart. Cut a piece of slate to fit the cracked piece an replace glass. Now, you have an old school tank. Welcome to 1950:D