I have faced this dilemma. Going away on a two week vacation, no fish care available. I have those dissolving pyramids, battery operated flake feeder, but nothing for my spiny eel who only eats live food or frozen bloodworms. So, I have used ghost shrimp and guppy fry to keep it alive. Not much different than my Platies dropping fry in the community tank only to be devoured by the angels and spiny eel, its just that this time I have arranged for it, and at a time that it will keep my fish alive and healthy. I have not done it any other time, when frozen foods are an option. Oh, and three or four of the guppies have escaped predation, and seem destined to make the transition from food to pet, and I have a neon tank that they might be happy in.