Like I stated....I am sure they probably do spawn in smaller tanks. I have just heard of the successful spawns taking place in BIG tanks. There may be no way to simulate tank size how they need it. It doesn't sound like water quality is the hitch point to me. Otherwise you could over filter and make the tank seem to contain a larger water volume with crystal clear water. But, it sounded like to me you needed more physical space for the females to get away and hide from male aggression. Big caves, lots of rocks, etc. Maybe if you had some really nice items for aquascaping you could partition the tank off into several areas each with a good hiding spot for females. Just a thought. Sully might have some input. I know he has Petros right now. Not sure if he has had any action or not. Thinking someone mentioned that he had his in a 180G or something like that. Good luck.