I was just thinking like some ocellaris clowns or mocha clowns and i had a clown goby and he never ate. And i had some yellowtail damsels and one was doing goof but then last week i didnt see him and haven't seen him since and i had got a domino damsel that i was told wasnt aggressive but he ended up picking on everything so i took him back.
Actually, I would suggest staying away from damsels and clowns.. Active swimmers, honestly, as they have tons of personality, a small either Niger or pink tail trigger.. Yes, they will get big, but.. They are hardy and very entertaining fish that love to react with you. Small angels, they can be tough because they love some sponge in their diet.. I have a spot breast, but supposedly, they can get decent sized also.. But she is a meat eater(well, honestly, proving to be anything eater) also..
My stocky anthias is pretty darn sturdy..
I'm trying to think what else that is sturdy but won't become a menace.. A goby/pistol pair, but be ready for tunnels..
Blennies also, and hawk fish.. Both entertaining!
A foxface also, just a small one, as they are algea killers! And are very, very easy..
Might want to consider some brackish fish like monos also.. But they can be aggressive towards one another.. And they eventually do get big..
I mentioned fish that get larger, simply because, if you buy them small, that will give you a year or two.. And honestly, if your still with the hobby by then(not to be a Debbie downer), your going to upgrade your tank, so they would make great candidates at that time, and you won't have to spend a ton on decent sized healthy fish..
Just an update. Ive got a pair of snowflake clowns, a weaver goby, and an aptasia filefish. Still looking for other fish or inverts. So if you have anything for sale that would be fine in a 40 gallon let me know.
I would add a few chalk bass. They're cheap, hardy, stay pretty small, reefsafe, colorful, get along with everything that won't eat them and are pretty active. I have two and they're awesome. Just be careful when you buy them. Stores tend to keep a ton of them together and they seem to be prone to ich aka cryptocaryon irritans.