[Myka]

I think you can easily house either a Kole or a Tomini tang in your cube provided you buy a small specimen to start with and you create a central rock formation that the fully grown tang can easily swim around in circles. That means you won't be able to fit as much rock as is typical in many reefs. Keep in mind also that your corals will grow out from this rock, and encroach on the tang's swimming space. I suggest you pick a small specimen because it will adjust to the abnormal swimming area much better than a medium or large sized specimen that may be quite used to swimming either the ocean or a longer typically shaped aquarium. The Tomini typically will grow faster than the Kole, but personally I like the looks and personality of the Tomini better. I would also suggest you add this fish last, and after the rock has sufficiently aged (especially if you are using diy rock), say 8-12 months.