for the past few weeks i have switched my marble goby over to eating red worms/ trout worms. i feed him as many as he is willing to eat in a day. which is one maybe two. he is 4 inches in a ten gallon, i have a twenty cycling now and a 55 that is on a stand but not filled yet. my goby has not grown hardly at all. but he may have gotten wider but not longer. water changes are10-25% every 3-7 days. are these guys slow growers. or am i doing something wrong?