I have a Biocube 6 gallon reef on my desk at work. While it is fun to stare at during the day, it is also a pain in the rear sometimes. You need to worry about flow, steady salinity (daily RO/DI topoffs, depending on temperature), light and imo, the most critical thing, a narrower "safe" temp band.
I have twin 18W PCs over mine and they work for rics, shrooms and zoos. I have a couple of small LPS (trumpet corals) and while they're still alive, they do not grow very much.
If you really like the idea of a nano reef, I'd stick with live rock, some shrooms and zoos. Feather dusters are also great for a low-light tank. The flow from the filter should be good enough for these guys if you position them correctly in regard to the filter outflow.
I'm not sure what the fan configuration is on the hex tanks, but having an incandescent bulb in there may worry me about temperatures getting above 85 degrees. If this happens, you will most likely lose any corals you have in there. They have thermostats that automatically shut things off when heat gets too high, but they're a bit pricey.
Get a small goby and maybe a peppermint shrimp, along with 2-3 snails. I have a watchmen goby/pistol shrimp combo in mine and love it. Tiny tanks are perfect for them as they'd get lost even in my 26 gal reef at home.
Get creative and go on nano-reef.com for ideas. It's a great site. I'm sure someone has even used this tank for a setup before.
Alternatively, planted tanks are also very cool.
EDIT: Sorry, took too long to type and John had already replied before I hit send.
