Ok missed that last question and on another site this is how I answer that. These fish need clean water. If you’re not up for the maintenance they may not be for you. I understand what you’re saying 6 in a 140 should be fine. But you know what happens. Dither fish,plants,more discus and before you know it the tanks overstocked.
Chatfouz im not saying you I’m saying in general. But even you will need to do the first month of water changes and if you get more your maintenance will need to be more.