I have had no issues moving fish around my eco system since all have been with me for a while or born into it. New stock always QT and hero. That's my opinion and I had no issues but others might differ. I even mixed my Stendker after a while since he has been with me over 2 years and now he is the proud papa of 100 plus fry with a nice Malaysian lady. Still I guess a hero can't hurt. I only have 5 tanks running but this is my experience. I would get a more knowledgeable member to chime in.