I have a few questions, here is the background. Im getting my tank squared away after losing most of my fish - not sure what the cause was, most levels checked out. Have had Cichlids for about 10yrs.

PH is currently around 8.6, ammonia and nitrite are fine, nitrate is high. Curretly have a 3" auratus (seems aggressive) and a 3" mix mumba born in the tank. Plenty of rocks and a sand / coral substrate. Looking to add more fish.

Do I try to work around these two or turn them in to a dealer and start new? Would love to go with Aulonocaras at some point.
Is 8.6 ok or should I try to get down to 8.2? if yes whats the best way?
Do I need to be concerned about the nitrate? should I get Nitra Zorb.

Any help with these questions would be much appreciated.