You can also get bloodworms, brine shrimp and daphnia jellied in handy little sachets; they seem to make less mess than the frozen stuff and you can handfeed the fish straight out of the sachet. Mine love their peas, frozen, slightly boiled with the shell taken off, and mashed up a bit (though guppies are quite capable of chewing bits off); they also eat spinach and chard, again lightly boiled. Alternating the above with tropical flakes should give a good balanced diet.