Hi.
I am setting up a mbuna tank at the moment.
I am using limestone rocks as they slowly increase pH, which for me I need as my tap is 6.5. You need 7.5 minimum really, but 8.0 - 8.5 is better. These fish need hard water, which again the limestone helps with. My tank is 260l and I have 40kg of limestone, which I am considering increasing to 60kg. I am using a sand substrate as the mbuna like to dig, so a soft substrate is less likely to cause damage to them when they dig. I have a bit of crushed coral mixed in around the back, again to help with pH level, then some crushed coral in my filter too.
I am new to these fish, but not new to fish keeping alltogether, so have some basic knowledge, but not as much as some on here, so theres some basics for you based on what I have done with mine so far and hopefully someone else will add some more for you.