Which fish to add?

[Bigals-nano-1]

I’m looking to add one more fish to my Fluval 13.5 gal tank which currently has two tank bred Ocellaris clownfish, 2 cleaner shrimp, 2 red legged hermit crabs, 5 nassarius snails, 4 sexy shrimp and a couple of turbo snails. There are also various corals in the tank and I have a short list of either a Tail spot Blennie, Royal Gramma, Bi Colour Blennie or a Yellow Watchman Goby. Which one do you think would be the best to add?

 

[vetteguy53081]

Firefish goby
Twin spot blenny
Watchman goby
Banghai cardinal