I would say they grow at an average rate. 1" per month would be fast, and anything less than 1/2" per month being slow. I bought mine almost one year ago. When I got him, he was 1/2". Now he's about 6. So mine grew around 1/2" per month. Beautiful fish though. Love them. Mine is a true texas cichlid. The 'green' texas should grow at pretty much the same rate though.