I've kept snowflakes for a short term in a 29 before, but don't recommend it. He's much happier in my 120, now. As for eating tankmates, they are crustacean eaters, so shrimp or crabs would be in danger. Fish should be fine, though predicting aggression in individual animals is always a throw of the dice. He may be the one snowflake with a taste for fish. Mine eats heartily on the shrimp I buy from the grocery store and competes with the niger trigger for chunks of it (they'll race to the food, but in the end some pieces will still be there when the frenzy ends, and disappear over the next hour or so).
Anyway, snowflakes are generally fish safe, but you might want to avoid sedentary fish like gobies or hawkfish.
HTH!
