EVERYTHING YOU NEED TO KNOW ABOUT THE FISHIES:
Naming a fish is the best way to ensure his or her death.
However, Fatfish is sanguine and goal oriented, where the ultimate goal is, obviously, happiness--which would be best manifest by eventually being big enough to eat littlefish; mediumfish is well balanced, except when he's got gas and floats weird; and littlefish is both miserly and acerbic due to his perpetual state of hunger caused by obsessive compulsive weight watching.