Great to hear that your 14 gallon bio cube is doing well! I also have one that has been up and running for 3 years now!
My only two suggestions are to perform a weekly water change and to get rid of the bioballs and replace them with live rock instead! You also do not need to purchase the skimmer they make for your size bio cube! IMO, it is a waste of money and not needed with ample amounts of live rock and surface area for both, aerobic and anaerobic bacteria growth and population.
I love it!
Best of luck to you and your inhabitants as well as here at Saltwaterfish.com!
Tom