Jarrod, patching it the way you are talking about won't work. The inside joint of silicone is not what holds the tank together, its' the thin film that is actually between the two panes that makes the seal. If you are already seeing penetration to three or four inches, then you are in real danger of a tank blowout.

The best advice I can offer is lower the water level in the tank to ease the strain, then use bar clamps backed up with 2x4's to help hold things together while you figure out what to do.

Trying to get any kind of seal with stock in the tank is a no-no. The VOC's coming off of the silicone will kill your animals unless you can keep it out of the water until completely cured (at least 48 hours, in my experience). Honestly, trying to rig a patch is just putting a bandaid on a bleeding artery. The tank is going to need to be taken completely apart, each piece of glass thoroughly cleaned, then rebuild the tank one pane of glass at a time. Sorry to be the bearer of bad news :*( If there is anything I can do to help, please let me know.

I do have an extra 110g tank that you can borrow if need be, and I am sure that members have tubs you can use as well. Good luck.