Clowns and catalina gobies have very different temperature requirements. Honestly, I wouldn't start with a biocube. I just started with saltwater a few months ago...my first fishtanks ever
Go with a 30 or 40 gal
...it'll end up costing close to the same as the biocube anyway, but they are way more forgiving of error and less demanding on time. I have a biocube 14 right now...just FYI, it only holds about 10 gallons; not much space. If I knew that prior, I wouldn't have bought it - would've went with the biocube 29.
Saltwater is definitely worth it though...the fish are amazing - so much personality and color!!