A Midas can be mean, but no more so than a Freddy or Argentea... I mean cichlids, for the most part, are unpredictable. I had a Midas (I will always have a Midas, lol) in the past that got along fine with its tank mates. I've also had a Carpintis (Texas) who was a complete psycho. All Amphilophus grow fairly quickly, not just Midas.
