First of all, what type of cichlid you prefer to keep? Lake of Malawi? Lake of Tangayika? Center American or Southen American? Asian?

You can add the dry coral or coral chips. (put the crashed coral chips into a bag.) then you can get the bag of coral inside your filter box. So that, the coral chips wont spoilt the setup of the tank.

Lake of Malawi or Tangayika biotope setup almost the same. You can just use the river sand or sea sand with some rocks. (remember must wash the sand) More coral chips you add in. The PH level will be higher.

If CA or SA, you can use the same sand bed. But with bigger piece of rock + drift wood. (I think your tank is suitable to keep CA/SA. coz they are huge.)

I was keeping Malawi cichlids inside my 100 gallon tank. The Mbuna breeding with fries. It is fun to have them and easier to take care of them. You just need to maintain the PH level and feed them twice per day. Dont over feed them.