So what's a minimum number for a shoal of Paratilapia sp in a tank?
For Paratilapia I got 3 females and a male which was peaceful for a while in a 6 ft tank..
But for most Madagascans, I prefer a shoal of 6-8 if possible.
I was part of a joint order to Old World Exotics, their minimum made it only feasible if a number of aquarists joined in.
My only part of the order were 6 Paretroplus nourisatti running @ $350.
Within a year, the male had killed all others in a 150 gal tank.
I believe lack of enough current contributed in part of the excess aggression.
Better luck with a shoal of 8 Paretroplus menerambo, until they outgrew the 150, (hitting almost 15") and started getting aggressive within the group.
I had the best luck with 6 Paretroplus maculates, because when they matured, and got even the least be testy, I moved them to a 400 gal kiddy pool.