Potosi Pupfish
Cyprinodon alvarezi
A fish extinct in the wild, kept alive by dedicated hobbyists worldwide.
About
The Potosi pupfish (Cyprinodon alvarezi) carries an almost unbearable weight for such a small fish. It no longer exists anywhere in nature. Its entire wild population, which was confined to a single spring system at El Potosí in Nuevo León, Mexico, was wiped out, and the species now survives only in the hands of hobbyists and conservation programs. That context matters, because keeping this fish is genuinely an act of preservation rather than casual hobbyism, and it's generally not recommended for community fishkeepers without a serious commitment to that responsibility. Males are territorial and need enough room to carve out their own patches of space, though multiple males can coexist in a sufficiently sized setup. Breeding groups are best kept as a species-only tank to give conservation efforts the best chance of success. Despite being listed as beginner-friendly in terms of basic water chemistry tolerance, the social dynamics and the ethical weight of the species make it better suited to someone who has done their homework. Physically, these are compact, chunky little fish in the classic pupfish mold. Active, personable, and surprisingly full of character for their size. If you're drawn to conservation-focused fishkeeping, this species is one of the most meaningful you can work with.
Similar species
Other fish you might consider
Good tank mates
Species that tend to coexist peacefully with Potosi Pupfish
From the same region
Share the same natural habitat. Great for a biotope-themed tank
Frequently asked questions
- How big does the Potosi Pupfish get?
- The Potosi Pupfish reaches about 1–2.5" as an adult.
- What size tank does the Potosi Pupfish need?
- A minimum of 14 gallons is recommended for the Potosi Pupfish.
- What water parameters does the Potosi Pupfish need?
- The Potosi Pupfish does best with a temperature of 63–82°F, a pH of 7–8.5, hardness around 5–25 dGH.
- Is the Potosi Pupfish aggressive?
- The Potosi Pupfish is semi-aggressive. It can work in a community with careful tankmate choices and enough space.
- What does the Potosi Pupfish eat?
- The Potosi Pupfish is an omnivore. It does well on a varied diet of quality flake or pellet plus occasional frozen or live foods.
- How long does the Potosi Pupfish live?
- With good care, the Potosi Pupfish typically lives 2-3 years.