Anyone who’s kept Rift Lake cichlids, especially mbuna, knows they can be rough on each other. This is especially true when your gender ratios are wrong, your species mix is wrong, your tank size is wrong, etc. In fact, cichlid behavior of most genera is often predicated on these errors. Regardless of how “perfect” your set up is, cichlids can be rough. However, they’re tougher than you think. Sure, a weaker or subordinate specimen can get dispatched pretty quick without you every noticing it, but don’t undersell their toughness.
If you observe your fish regularly, you’re bound to hear them bounce off things when they scramble. In my two largest tanks (one for Tangs and one for mbuna), I have copious amounts of rocks and caves. When my fish scramble, either because one of them has “signaled” trouble or a sudden movement by me frightens them, they will bounce off everything in their dash to find a hiding spot. Even a small fish bouncing off a rock or a tank wall at full speed makes noise. Imagine if 8 or 10 of them do it at the same time. Yet, it is very rare that any fish loses scales or otherwise shows damage. In fact, I very rarely lose fish, and it’s never a result of scrambling for cover.
Cichlids are tough and can take a temporary beating, but don’t use that as an excuse to mix fish that you shouldn’t or to not provide as ideal a set up as you can. A temporary physical encounter, with each other or inanimate objects, isn’t the same as a sustained beating. Don’t be too alarmed when you hear your fish banging into stuff as they jet off and out of your view.