frogfish are easy to feed. until mine learned to take frozen, I offered gutloaded ghost shrimp and guppies, acclimated to salt water. the occasional small damsel is always apprecieated.
all of mine eventually learned to take frozen from a feeding stick (though one took over two years, so you can never count on this).
once eating frozen, I offer pieces of scallop, shrimp, a selection of ocean nutrition gel cubes (which really help with dietary variety).
I've noticed growth and color is better with the frozen food diet. you can keep anglers long term with live foods, but getting them on to frozen is best.
I have several species tanks - angler, mantis, seahorse. I love all of them. that's why I have so many (too many!) tanks. I can't give up any of them.
If you like Rhinopias, and want something cheaper, easier, smaller that can be kept in groups, consider Hawaiian leaf fish. they are exotic, gorgeous, different. mine are in with my seahorses. I've had the leaf fish and seahorses for several years. the leaf fish WILL need live food. I have never been able to train a leaf fish to take frozen (again, gutloaded guppies and ghost shrimp). they'll eat any shrimp in the tank and any tiny fish (like neon gobies).
if you are willing to upgrade your species tank in time, I'd consider an undulated triggerfish. it's pretty clear you can't keep them with other fish long term. They are gorgeous and don't get over a foot long. You could keep a juvenile in a 40 gallon tank for some time, but would eventually need to go with a 75 or larger.
another "pet fish" for a smaller tank might be a toad fish - I had an orange gulf toadfish (Opsanus beta) in a 20L on my desk at work for years. it got to be quite personable. it ate anything and everything I offered.
I have a green wolf eel blenny that is full of personality. I have it in a 55 with a waspfish, as well as two fish I'm growing out for a bigger tank (niger trigger, blue spotted rabbitfish). they all get along great, and the eel is really ugly/cute. There is a reefkeeping article on breeding them. I'd try pairing up some wolf eels and breeding them.
sorry for the long post. I had a lot of ideas... trying to decide what to do with my empty 40g breeder as well.
