New to this forum but I have had fish for the past couple years in small tanks , about 5months ago I set a 90 gallon up and my current stock is a jack Dempsey , Vieja Argentea , and I just got a fire mouth this week , both the jack and argentea are between 5 and6 inches the fire mouth is smaller than them and the argentea picks on him a bit especially when feeding the firemouth has barley eatin cause he keeps getting chased away I was thinking about going back to my lfs and picking up another firemouth would this be a good idea and is my 90 too small for that many fish?