Depends on what particular cichlids you will be keeping. I believe a test kit such as API freshwater master kit will tell you what the Ph of your source water(water used for aquarium) is. You may not need a substrate such as argonite or crushed coral. You may be able to simply add crushed coral to the filter to achieve the Ph needed but again, ,this depends on what species of cichlid you will be keeping and the Ph of your source water. I would maybe run some of the water I will be using for this aquarium into a bucket and let this bucket sit overnight. I might then test the Ph of this water and that would tell me what my Ph is . From there I would simply google information on possible cichlids that I might be interested in to see what species would be comfortable with the Ph that I have and go from there. A cichlid substrate will mean that this tank will only be suitable for cichlids so to make the tank suitable for other species should you decide to change your mind at a later date,,, would mean that the substrate would need to be removed lest the Ph be too uncomfortable for many other freshwater species. Higher Ph values usually are associated with slightly harder water while lower PH values of 7.0 or below are usually indicitive of softer water. ALWAYS better to try and purchase fish that will be comfortable in your water than trying to adjust the water to suit the fish.