Overstock, understock?

IMO, understock only works with proper M/F ratios and limits the number of fish to a low level.

Overstock cuts the aggression on an individual but interfere with breeding and saving fry if that is your intent.
 
^ that's what I think, as a very new fish keeper.

I think one of the attractions of mbuna is you can keep a such colourful, active and interesting display of many fish successfully by overstocking.
 
I am a fan the overstocked Mbuna tank. It seriously cuts down on aggression, and it makes an active and beautiful display.
 
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