In a 90 gallon tank, a fish might not reach 12 -14 inches, but that doesn't mean it's going to be significantly stunted if it maxes out at 10 inches. Not all fish have to reach the max size - they don't in the wild. Various factors will influence how big a fish grows just like with any animal. A barn yard cat for example won't reach the same size as a cat living indoors and getting the best of food, doesn't mean the outdoor cat is automatically malnourished and mistreated.