Pterophyllum scalare are found normally in smaller groups of five to ten within a large Discus group and are, after Geophagus/Satanoperca/Biotodoma species, the most frequent mates of Discus. P.
Males of the larger gymnotids can sometimes be aggressive, so be careful about mixing this with similar fish. Robust but placid cichlids, such as Heros, Acarichthys or Geophagus, should be safe ...