It depends, good water quality and how often you feed them will have the greatest impact along with tank size (effects water quality). A Umbee will not grow 1" a month in a 10 gallon tank. A Umbee in a 400 gallon tank with weekly 50% water changes and a good diet (not over feeding) will have a fast growth rate. Not saying you need a 400 gallon for a 3" Umbee, just saying. It's always rewarding to have a 3" fish grow into a monster, still takes time though.