CephBase had 1000's of predation records. Among them was a single record of algae in a ceph's stomach. The papers authors and I both believe that this was an anomaly. As far as I know, all cephs are predators with most preferring live prey.
You might as well be asking why people top off at gas stationssnowmaker;155404 said:I have often wondered why some aquarists will feed their wet-pets terrestrial foods like spinach for herbivorous fishes and garlic, of all things.