Reverting divided tank?

[Hellsrage]

You can use one of these type of razor knives to carefully clean silicone off the glass



And always use a new blade, a sharp blade is safer and makes the job easier.
I didn't know exactly what these knives are called so I figured that a picture is worth a 1000 words LOL

That would be a single edge razor attached to a holder. I just recently bought one for $4 at Home Depot, came with a nice plastic holder and 10 replacement blades. One tip I can give you is change the blades often. Like Louis said it really helps, I changed blades about 5 times when I removed the old silicon from my 20 gallon tank.