My afro grew from 2 inches to 13" in a year in a 75g tank. Now he is in a 180g. Ill probably upgrade in about a year or so to a 7x3. He has only grown to 14.5" in the past 3 months and i only expect his growth to slow more as he gets larger. Id estimate it takes about 2.5-3 years to reach 24"+.