I feed my loaches cucumber at least a couple of times a week. They all attack the same peice (dispite the fact I put 3 pieces in) and keep going till all the middle has gone then they move on to the next piece.
Meanwhile the plec moves in for the kill and promply clears up the remainder including the skin.
They love cucumber but also like shelled peas, sprouts, beans, bloodworm, flake, potato and brine shrimp.