cichlid newbie advise wanted

I have 4 tropical species and community tanks but no cichlids. Having found
a spare corner for yet another tank, I've decided to try Malawi cichlids.
I'm in the process of setting up the tank and like to know if I'm doing it
correctly. It's a 35gal tank. I've put a find layer of silicon sand on the
bottom topped by coral gravel. the reason for this is that my normal is ph
is extremely low - under 6.6. in the main trop tank, I add coral to the
filer and the ph has gradually increased to 7 but I know cichlids like it
higher than that. I know I could add chemicals but am reluctant to go down
that route unless really needed.
I've added lots of large ocean rock and lava rock with plenty of hidey
holes. No plants as I know that's not their normal habitat. filtration is a
fluval 4 plus, again with coral added and there's also a airwall. Temp at
moment is set to 28.
I've added a sponge from one of the other tanks tot he filter and I've also
added the tank water the other filters have been cleaned in so there is
plenty of filter material. The water is hard (around 200ppm) BUT it is also
low KH (around 40ppm). I'm hoping this will increase as coral does it's bit.
Does this sound as if I've done this set up correctly? And would I be able
to get a couple of fish at weekend? which brings up another point - I know
you're not supposed to add cichlids to an established aquarium so how do
you stock gradually? I don't want fights breaking out each weekend!
Many thanks for any advice.