Anglers honestly do best in species/specimen only setups. They can eat fish twice their size easily, which normally kills them, BTW. Additionally, they're often picked on/at by other fish, esp. those that browse on the rockwork.
They will eat ornamental crustaceans (shrimp, crabs) with the exception of hermits. Snails are fine with them, however.
As for keeping them, once you obtain a "good" specimen, they're pretty easy to keep...they only require feeding twice a week as adults, or every other day as juvies. Feeding them too much is bad for them, as they have such slow metabolisms, large items/amounts of food will actually begin to putrify in their GI system before it's digested, which kills the fish.
Anglers are also prone to a little-understood malady known as SAD (sudden angler death), where a seemingly fine fish will dart around the tank, bloat, and float (and of course die), so you may go thru a few fish before you find one that "sticks".
HTH