Dividing a tank?

[Jaws]

I plan on setting up a refugium and a frag tank in the next little bit and I'm just tyring to plan how to do it. One of the ideas was to set up two 25G tanks side by side using one as a refugium and one as a frag tank. If I could, I would like to be able to separate the frag tank into two sometimes to use as a quarantine tank. I live in a condo so space is limited and anytime I can combine things it works in my favour. I'm obviously reaching but I thought I'd throw it out there for fun and see if anyone had any ideas.