If you are goign to set up a sump for that small of a tank, I would highly recommend you do the refugium version as seen in that photo above. I use an extremely close version of that on my 55g and it has made the hobby 10 times easier for me, mostly in part to the lack of algae problems I have now. And the added pod populations to my tanks make a massive difference in fish behavior and health. Nice, Fat mandarin, scooter, wrasses, ect. ect.
Michaeldaly hit it on the nose with the sump description, just a simple way to increase overall water volume, which gives you more room for error with water quality, and allows you to hide most the equpiment from the display tank.
A refugium does the exact same thing, and then some.