Max Size: 6cm

Dusky Millions Fish (Phalloceros caudimaculatus)

The Dusky Millions Fish is attractive, hardy and relatively easy to breed. As a result, they are reasonably popular in the aquarium hobby. The Dusky Millions Fish is best kept in a species-only aquarium in a group of 6 to 8 individuals, ensuring you have two to three females to every male, as this will stop any single female from taking the full extent of the male's continual harassment.

These fish are peaceful, so you could keep them in a community aquarium alongside other peaceful species that also appreciate cooler water conditions, such as Danios, White Cloud Mountain Minnows and Ricefish. However, you should avoid housing them with species with intricate finnage or much larger aggressive fish that may intimidate or out-compete them for food.

These fish prefer a heavily planted aquarium with gentle filtration and water movement to mimic their natural environment. It would be best to choose robust or fast-growing plants, as many soft-leaved plants will be grazed upon; however, this may not necessarily be a problem if they are well fed. Floating plant species such as duckweed or water lettuce may be used to help dim the lighting in the aquarium.

The Dusky Millions fish is very sensitive to changes in water chemistry; therefore, any adjustments in parameters must be carried out slowly. It would be best if you also took care when performing water changes, frequently perform minimal amounts, but gradually add the new water. For this reason, this species is only recommended for advanced aquarists.

The Dusky Millions Fish has a silvery body with a small, dark, vertical elongated mark under the dorsal fin and black patches on the fins. The male bodies are distinctively speckled with many irregular black blotches and spots, whereas the females only display a few. In addition, you may find some individuals with a yellowish hint in their bodies.


Dusky Millions Fish
Dusky Millions Fish
Quick Facts
Scientific NamePhalloceros caudimaculatus
Year Described1868
Other NamesSpeckled mosquitofish, one-spot livebearer, Speckled Livebearer, Leopardfish
OriginsArgentina, Brazil, Paraguay, Uruguay
Aquarium LevelAll Levels
DifficultyIntermediate - Advanced
Best kept asGroups 6+
Lifespan1 - 2 years
Water Parameters
Water TypeFreshwater/Brackish
PH6.0 - 8.0
GH5 - 20
TDS90 – 447
64 - 72℉
17.8 - 22.2℃


In the home aquarium, the Dusky Millions Fish 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.

Sexual Dimorphism

It is very simple to differentiate between the male and female Dusky Millions Fish. The females are much bigger than the males and have fewer blotches. In contrast, the males are smaller, have more speckling than the females and possess an evident gonopodium.

Other Livebearers of interest

Cardinal Brachyrhaphis(Brachyrhaphis roseni)
Humpbacked Limia(Limia nigrofasciata)
Merry Widow Livebearer(Phallichthys amates)
Mollies(Poecilia Sphenops)
Platies(Xiphophorus maculatus, Xiphophorus variatus)
Spotted Skiffia Multipunctata(Skiffia Multipunctata)
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Date Added: 16/06/2022 12:50:37 - Updated: 16/06/2022 13:44:58