Coralline repels algae anchoring, it also leaves a nice depositional record of your calcium and alk consistency when no white banding exists. it is also street cred. coralline is also the universal proofer for cycles: any surface underwater long enough to dot in coralline is cycled for nitrifiers, and can’t work in the opposite direction (new coralline never manifests before nitrification ability) It’s part of visual cycling life forms we can use to replace test kits.
the presence of coralline turns all stuck cycle threads into no longer stuck, quit relying on api.
it beckons coral larva to attach for growth via chemosignaling so caking your whole reef in reproductive stimulants must be good and very 1997. I’m not impressed by systems lacking coralline you should have to shave it like a five o clock shadow in the reefs that work best.