Max Size: 4cm

Blue Purple Emperor Tetra (Inpaichthys kerri)

Blue Emperor Tetras are active peaceful shoaling fish. Unfortunately, Blue Emperor Tetras do have a somewhat undeserved reputation for fin-nipping. However, this type of behaviour only really manifests if you do not keep them in sufficient numbers and there are not enough visual barriers amongst the decor.

You should always maintain this species in good-sized groups of around ten or more individuals. Not only will this make the fish feel more secure, but it will result in far less hostility between the males, and it will create a much more effective and natural-looking display. In addition, rival males will show their best colours when displaying at one another.

Ideal tankmates for Blue Emperor Tetras should be small and peaceful. These could include Corydoras Catfish, small Dwarf Cichlids such as Mikrogeophagus or Apistogramma, Pencilfish, and some smaller suckermouth Catfish. These fish will also do well with Rasboras, smaller Gouramis and peaceful Barbs. It would be better to avoid larger, more boisterous tankmates as these Tetras are easily intimidated. You must pay much attention to water quality because Blue Emperor Tetras can be sensitive to high nitrate levels and fluctuations in water chemistry.

The best aquarium setup for these Tetras would include plenty of driftwood. This will create shady areas for your fish and gradually release tannins from the wood, which will help acidify the water whilst giving it a natural, clear tea colour. Peat filtration can also help in this regard. Although plants are not found in abundance in this species natural waters, a moderate amount of planting will be appreciated and will help make the fish feel more secure. Lighting should not be too bright, and a darker substrate and background will help show off their pleasant colours.

Male and female Blue Emperor Tetras differ in colouration. The male's entire bodies are light purplish-blue except for their stomachs which are beige. In addition, they possess a thick iridescent dark blue stripe that extends from the snout through to their eye and the caudal fin. The male's dorsal fin is elongated, and their adipose fin is blue. The other fins are transparent except for the pectoral and anal fins that also have a hint of blue.

In comparison, females also have an elongated dorsal fin; however, their adipose fin is usually a reddish orangy brown. The females also possess a thick black line instead of blue, and the area above it is beige with a silvery-blue sheen. In addition, the belly is white and occasionally has a silvery sheen, and its fins are transparent.


Blue/Purple Emperor Tetra
Blue/Purple Emperor Tetra
Blue/Purple Emperor Tetra
Quick Facts
Scientific NameInpaichthys kerri
Other NamesBlue Emperor Tetra, Royal Tetra, Blue Kerri Tetra, Purple Emperor Tetra, Regal Teta
Aquarium LevelMiddle - Top
Best kept asGroups 10+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH6.0 - 7.5
GH3 - 12
73 - 79℉
22.8 - 26.1℃

Natural Habitat

Madeira river tributary


In the home aquarium, the Blue Purple Emperor Tetra will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Tank Mates

2 interesting tank mate ideas for the Blue Purple Emperor Tetra could include:

Cardinal Tetra(Paracheirodon axelrodi)
Peacock Gudgeon(Tateurndina Ocellicauda)

Sexual Dimorphism

It is relatively straightforward to distinguish male from female Purple Emperor Tetras. Mature males are usually more colourful and of a slimmer build, are larger and have a rounded anal fin. In contrast, females are far less bright, stockier in body shape than males and have an angular anal fin.

Other Tetras of interest

Adonis Tetra(Lepidarchus adonis)
African Moon Tetra(Bathyaethiops caudomaculatus)
African Red Eyed Tetra(Arnoldichthys spilopterus)
Arowana Tetra(Gnathocharax steindachneri)
Black Darter Tetra(Poecilocharax weitzmani)
Black Line Tetra(Hyphessobrycon scholzei)
View all Tetras
Date Added: 29/07/2021 15:46:48 - Updated: 22/11/2021 16:59:24