I had the red fir fish and it survived the change frorm a 38 g to a 10 g to a 20 g, all changes were done in a matter of hours, and i had him for about 8 months until, tank crashed...And the purple one i still have and i've had him for about 3 monhts so far...I feed formula one pellet, but his favorite food is definetly frozen krill!! He loves it!!