cutting a 30 inch tall tank to 24 inches tall.

[lastlight]

Check the beginnings of Dez's thread. He did a lot of this type of dremelling. Heck you could just do a coast-to-coast 6" down and drill regular bulkheads into it. Sounds like you want to not have it look silly as well but a canopy could easily hide a 6" rim.

[Dez]

I would maybe use masking tape to cut down on the shelling
Of the glass. Then maybe use you skill saw idea with lots of water. I just used a regular diamond blade from totem on my grinder.

[tinman]

you could rent a wet saw from home depot if you were taking the tank apart.