There are so many choices of gobies and blennies that will stock well in a 40 breeder. Also have several options in the basslet/gramma family. A pistol/goby pair would be good in that size tank (assuming your not going bare bottom) You also can look into a flameback pygmy angel if ya wanted, pretty well behaved and stays small, also look at blue reef chromis for some color/movement you normally get out of the tangs and schooling anthias you couldn't add. Another good option is a longnose hawkfish, geometric Pygmy hawkfish, or possibly a flame hawkfish. There's lots of cardinal fish out there... Bangaiis and PJs are common, and the Orbic, Blue-eyed, or ORA black cardinals are great too. And if your not against it, you can try a dottyback. Great colors, just have been known to be aggressive, so add him last, and a little jumpy but not more than a firefish goby.
I've got a clown, a yellow candy hogfish and a scooter blenny in my 30breeder. I've added 4 different wrasses and the hogfish has not welcomed any to the tank, just nips them constantly when they are out. 2 have been returned to the store, the other 2 never made it (poor possum wrasse) I absolutely love my hogfish, but add him last and with caution if you change your mind on it lol.
