For disassembling tanks, I usually use leather gloves, razor blades, and fishing line. Acetone works best for dissolving and cleaning off old silicone.
I feel like some have encouraged a full rebuild of this tank without mentioning a lot of the work that comes with it. Ime a reseal is not difficult, but actually building a tank is somewhat more. You're gonna need some more tools and materials to build a quality tank. Research and planning at this stage is a must for you.
First thing I would do is build some proper stands for your tanks. That table setup is cringeworthy lol