In my personal opinion, the less supplements or things you have to add, the more stable the tank will be in terms of water parameters and happier your fish will be. In regards to CC vs. aragonite sand, I've used both, and both can accumulate debris and provide a location for it to break down, thus raising the level of usable nitrogen in the system. The primary difference has to do with the difference in size between the two substances. CC is larger (gravel sized), and thus provides larger openings for substances to settle. Aragonite on the other hand, has a much smaller grain size and thus makes it harder for things to settle into the substrate. It does not prevent this entirely however, and so if you are not maintaining the sandbed, it will create the same issues as the CC. Both substances break down over time and help keep the pH at the slightly higher level that is favored by the mbuna. Regardless of which substance you choose, both will require regular maintanence.
