[confuted]

Whoa there.

Cutting the rim off ... sure.

Trimming the silicon too? Seems like you're inviting disaster. If you're going to go through all that work, why not spend a little extra effort to fully break the tank apart, clean the glass, and apply a stronger grade of silicon? I'd trust it a lot more than a hacked up version.

 

[confuted]

I'm far from an expert on this, but my understanding is that the silicon that provides the strength in a joint is only that which is in the thin layer between the two pieces of glass. At most the fillet of silicon in the corners helps prevent leakage. Silicone sealant is very flexible, so a thick gob will easily deflect under stress, but a thin layer just barely deflects under stress.

I'd assume you'd want to "prevent leakage" on an aquarium...