I cut the cucumber 3"long, half lengthways I then weigh it down and drop it in the tank. Loaches and plecs love it and when they are finished the mollies and guppies dig in, when they are finished the snails attack it! My plec is 12" long and it leaves a furrow right down the middle of the cucumber - quite cool!
I put the frozen peas in a cup, pour boiling water over them, leave for only a couple of seconds, empty out the water then sit for ages shelling the peas. squash them together and drop into the tank. My cats sit for ages waiting for me to do this as they love the shells - weird!