In my experience, it is. Have you figured out how to seal that joint?

First step is ensuring that I get that chamber totally dry. Then get in there with a scalpel to remove the old silicone, then put down a bead of new silicone.

This will all have to be done by feel since the chamber is too small to look into while I have my hand in there.

Orca underwater Silicone works. Use clams to ease pressure of full tank (compress glass) let sit for 24 hrs, works well have used it several times on old hagen tanks!

Yes, multiple attempts at sealing the leak before I got a dry tank. As mentioned by others, silicone does not stick to cured silicone so you need to cut a lot out and make sure the surfaces are really clean. +1 on the comments regarding the other seams potentially being ready to go as well. I had a stand go on a 75G FOWLR tank in 1997... final insurance tally was $66K. I would expect more than four years out of a tank so there might be other issues with it. If a leak isn't going to cause a lot of damage to your house you might want to risk it, but perhaps not. The tanks I have resealed are on a cement floor in my basement so no real risk to damage the house,
Dan

We have Orca underwater glue available, it works great.

http://www.royalaquariums.ca/p/464/o...ter-glue-black

This stuff is pretty good for underwater glue, but not for repairing a blown seal on a tank. If a seam is leaking, it needs to be repaired properly.

You need to cut the silicone away and clean it with alcohol to completely dry the surface and remove the water that is in the joint as well. Next, fill the joint but ensure there are no air bubbles whatsoever. It is best to do with 2 people. 1 person filling and the other person watching from the outside to ensure no air bubbles are present while caulking. Use a silicone caulking applicator to push the silicone in place and create a nice clean bead. Wait a good 3 days before putting water back into the tank.

Honestly, a new tank is all ways a better option than trying to do repairs...