They are ominvous and they awill pretty much eat anything if it fit in their mouth. I pretty much share all the food I eat with them. I sometime drop any meat I eat. Shred of chicken, scrap of beef, bits of shrimp, boiled green pea, crumb of the bread. Oh they like yolk from the hard boiled eggs, adults or frys. You can almost try anything just don't feed same thing all the time. And no seasoning on their meat or seafood. And try little amount first and see how they like it first. So there are not much leftover that foul water.
I even tried little bit of banana and my Tetras and Corys cleaned up. Now I am start trying the human baby pastely food. Like squarsh, sweet potato. Since someone mentioned that some famous Tetra breeder feedthe "butter nut squarsh."
Of course I feed usual fish food like flakes, pellets and live culture most of the time.
So I guess, just like us. They seem they enjoy the variation but the moderation is the key IMO.