What Should I Use This Spare Tank For?

[Bugboy2020]

Hello Reefers! I'm setting up a 5 gallon reef tank, and lately I discovered a lost relic of the past: My first fish tank. It's an older version of this http://www.walmart.com/ip/Hawkeye-3-Gallon-360-Aquarium-Fish-Aquatic-Pets/13448744
So! What should I do with it? Make it a sump? Refugium? Auto-top off? Other ideas?:idea:

 

[Fish doctor]

The first thing I would do is check it for leaks. Sometimes if a tank sits for some time, it may leak. At least that's what happens to me. If it checks out, I would use it as a quarteen tank.

 

[Bent]

Man-tis! Man-tis! Man-tis!

G. Smithii are good for nano tanks.