BLUE EMPEROR TETRA (Inpaichthys kerri)

A peaceful species that will not compete well with more boisterous or much larger tankmates. Ideally, it should be kept with other South American species, which can include small tetras, pencil fish, hatchet fish, Apistogramma or other dwarf cichlids and peaceful bottom dwellers such as Corydoras and Otocinclus. It will also do well with smaller gouramis, rasboras and peaceful barbs.

It has a bit of an undeserved reputation as a fin nipper. While it is certainly capable of this sort of behaviour, it only tends to exhibit it when kept in insufficient numbers. If a group of half a dozen or so is purchased, any aggression is usually restricted to conspecifics. Although it doesn’t shoal particularly tightly, it definitely fares best when maintained as a group, and rival males will show their best colours when displaying at one another.

https://www.seriouslyfish.com/species/inpaichthys-kerri/