I can't speak to Kribs or Acaras, but I would never put a rainbow with dwarf cichlids or keyholes. My rainbow is the most aggressive fish I have ever owned and is actually far more aggressive than my convict or firemouth. He would kill any dwarf cichlid in a couple of days or less. I realize that each fish has its own personality and you might get lucky with a calm rainbow, but from experience it's just too risky. I agree with BC in SK about mixing that combo - I think they would be fine despite being from different parts of the world. I have an African with my central American fish and have had no issues. Apistos would go fine with Rams, Keyholes and catfish. And yeah, I love apistos too. They are on my wish list. Good luck.