in a couple of years im planning on upgrading to a 50ish gallon tank cause i know the hawkfish cant live in the 20g forever im gonna have a mesh lid so the hawkfish cant go out for safety reasonsmatters the size of the flame hawk. my friend has one that decided to just live in the overflow box for whatever reason lol. everytime he takes it out it just jumps back in. they dont move much but as im sure you know, can eat smaller fish. you are doing a great job asking. it isnt the best fish for this size aquarium but can be added if u intend to upgrade