I'm a big fan of the Kole Tang myself -- looking to add one to my 75 when I get it running... Average max length, at least according to FishBase, is a bit closer to 5.75" -- tiny compared to most tangs, and they're also of the combtooth variety, so they scrape a lot more of the filamentous algaes from rocks, about as voraciously as Lawnmower Blennies

With twin-spot gobies, be aware that they have a typically abysmal keep-rate in aquariums, unfortunately... they are typically paired on the reef, but rarely imported as a pair -- and typically will just waste away when their mate is gone...

The two gobies listed should be able to co-habitate, esp. in a larger tank, but do know theres always a potential for aggression when adding multiple gobies or blennies -- very territorial fish, they are Since the gobies are from different subspecies of gobies, there shouldn't be a problem, but it can never be guaranteed..

Otherwise, sounds great Well planned

-Corruption