My Flame Gourami will eat blanched lettuce if I give it to him in small enough pieces for it to swallow whole, along with peas. I also get a knife or something and grind up part of an algae wafer into pretty small pieces and it likes those too. Other things in it's diet are bloodworms, flakes, shrimp pellets that I break into small bits, fruit flies(when I get a chance), and I even caught him eating a betta bio-gold pellet thing that my betta didn't find quick enough.
These are foods I accumulated and tried when I got a few extra bucks to pick up something new. I wouldn't go out and buy everything at once. Just get something every once in a while that is diff. and see how it likes it. It may not realize it is supposed to eat it at first, like my Gourami was with lettuce.