I think angel fish require live plants to live in (not REQUIRE, but sorta need...)
Im not really sure, but its good to have them in there.
Id say get some anarcharis, its a floating plant but you can tie and anchor it down, too. Java fern can be tied down to stuff and rooted eventually, so can annubias (all kinds(?)). Theyre good plants that dont need anything special. Id recommend getting florescent lighting to aid in their growth, but they dont need too much light.
Anarcharis sucks up ammonia like a champ.
Hornwort isnt too bad, either. It grows like crazy, but sheds its nettles so you'd have to clean up after it when they fall off, because its not good to leave in. Wisteria, too.
Id recommend getting some sort of liquid fertilizer to add to the tank once in a while, to keep things growing and green. Its not too expensive and you just drop it in.
Pics when your tank is up!