Heres what ive got in my 37g mix reef-
1 flame angel (i wouldnt get any dwarf angel in a 40g though, he will pace the tank like a mad man, im moving this guy to my 60g cube)
1 valentini puffer (will nip at LPS
but hasnt attacked my softies or SPS
A pair of purple fire fish
1 starry blenny
And my invertebrates-
1 caribbean porcelain crab
1 emerald crab
30 assorted hermits (dwarf zebra,red leg, blue leg, and 8 electric blues)
7 red bandit trochus snails
4 nassarius snails
1 snowball urchin
1 blue tuxedo urchin
1 cleaner shrimp
Many options is that size tank. Clowns will be fine in that size, i wouldnt try multiple gobys in one system. How about a yellow watchman goby and pistol shrimp pair? I have on in my 20 long with 2 ocellaris clowns and never have any problems.
Thats my yellow watchman goby. Make sure to have a tight fitting lid though because they will jump if given the chance. I use plastic wrap from the grocery store and triple wrap it to absorb and jumping by the goby or other fish.
How about a fairy wrasse aswell?
Gives a pop of color to the tank depending on which type you get.