We have had our 4ft african tank running now for nearlly two years. NEVER an issue with it at all. Occassionally a bit of aggression but nothing to bad.
You will find they are better kept in a high volume of fish as this disperses a lot of the agression.
I have sand in the bottom of ours and they are always renovating it.
They dig and dig.
Our sand has in it marble too and naturally has a high pH so we dont need to adjust it, ever.
The only thing you have to remember is to put the rocks firmly into the sand coz they dig under the rocks and they can move the rocks!
Lots of hiding holes are needed aswell
We have a big ship wreck in ours they swim in and out of and lots of caves.
The only issue with sand is when they throw it around it can make the water mucky for a bit till it settles down. But its awesome to watch
Definantly talk to your fish supplier about temprement and what other cichlids go with what you want, as some dont like others.
We actually have a couple of south american cichlids in with our africans
