Well since this topic got brought back up....
My Petsmart Midas seems to be a runt. He is a male, very thick, well proportioned, not stunted or short bodied at all; but just has not put on as much size as I thought he should.
Its been 15 months now of heavy feedings (Omega One pellets, Algea wafers, NLS, earthworms, nightcrawlers). 3 water changes a week of at least 1/3, in a 60x18 footprint 120g heavy filtered tank with water temp kept at 80.8 deg. And he is now a whole 8.5 - 9" and has been that way for about 6 month's now. He has increased in girth but overall length has remained the same.
Interestingly the sign in store says that the Midas only gets 8" where the on-line info I believe says 10". When I stopped by recently and spoke with one of the more knowledgeable staff members about my Midas, she replied that 'that was normal, that the fish breed for Petsmart are smaller types and will max out at around 8".' So I am continuing my routine and giving it another month or so to see if he increases in size at all otherwise I will replace him with something else. After all I was trying to get a "Monster" not a "mini-monster"!