Sorry, i misread your initial post.

If you already have a controller then its up to you if you NEED to upgrade. Based on your comments i doubt you would. I mean i wouldnt run a tank anymore without a controller in general. Be it APEX or not.
PS, coincidentally, my APEX decided to take a dump on me this morning. It was giving me some false PH readings of like 16 and i rebooted it and not it wont turn on. LOL. Didnt have time to futz with it this morning so i hope its nothing major. Im going to try to upgrade to the latest firmware.