you will not be able to set up a pod population large enough for one. and i know you said you were going to get one that eats prepared foods....
make sure, if you end up getting one, that you SEE it eat prepared foods and that you add vitamins to its diet.
however, even though i said the above, i still do not believe that it is necessarily ethical. amandarin is a fish who constantly hunts for copepods arounds tons of rockwork. in and out of caves.ledges. everything. They skip around and get the exercise that they need. It will be like putting a hamster in a little cage like that without an exercise wheel. the hamster will get unhealthy and die prematurely even if it is being provided with the food that is necessary for him to survive