Adding coral doesn't make a tank brackish, it's often used as substrate (crushed to gravel or sand) to buffer the water against reductions in hardness and pH.
Purple's right - you must get specific information about your fish before the right conditions can be recommended. West African riverine cichlids would require different conditions to those from the Rift Lakes, this before you even consider that they might be from another continent.
Great name, fishtank, how did you come up with that?
;-) just teasing mate!!