The eel will outgrow a 29, quite probably after snacking on the swordtail fry. Otherwise, frozen bloodworms and occaisonally brine shrimp would be a good diet. When it grows large enough, earthworms would probably be eaten as well. They're a river species, water conditions aren't critical as long as you avoid extremes or sudden changes in pH, etc.
I've seen him chase some of the swordtail fry, but so far they're all outrunning him. I wouldn't mind if he made snacks of them. He's very interested in the adult fish, but doesn't have any chance of catching them.
He seems active and healthy, so I guess he's okay for now.