I have my dovii pair in a 120 right now, male is about 8" and female is about 11 or so. They're in there with a common pleco who takes no **** from nobody lol. Eventually their tank will be upgraded but at the time being they get along great, and still have plenty of swimming room. Call me crazy but I see no problem in keeping them in that tank size until 14" or so, as long as they both get along fine.