Least Killifish tank mates
Heterandria formosa
5 rated pairings from the Least Killifish care guide. Compatibility here means water, temperament, tank zone and adult size all line up — the note on each card says why. Least Killifish needs at least 5 gallons on its own; every companion adds to that.
Excellent matches
3 · Same water, complementary zones, no conflict.
Endler's Livebearer
Poecilia wingei
10 gal min · 1.5" adult · Peaceful
Similar size, peaceful temperament, and compatible water parameters make them ideal companions
Otocinclus
Otocinclus vittatus
10 gal min · 1.5" adult · Peaceful
Peaceful algae eaters that thrive in the same cool, planted nano tank environment
Ramshorn Snail
Planorbarius corneus
5 gal min · 0.75" adult · Peaceful
Peaceful scavengers that help maintain water quality without threatening fry
Good matches
2 · Compatible with normal care — watch space and numbers.
Red Cherry Shrimp
Neocaridina davidi
5 gal min · 1.2" adult · Peaceful
Small shrimp won't be harmed; they occupy different ecological niches and help with algae control
Pygmy Corydoras
Corydoras pygmaeus
10 gal min · 1" adult · Peaceful
Tiny bottom-dwellers that won't compete for food or space in small tanks
Also recommended alongside Least Killifish
Species whose own guides list Least Killifish as a tank mate.
White Cloud Mountain Minnow
Tanichthys albonubes
10 gal min · 1.5" adult · Peaceful
Clown Killifish
Epiplatys annulatus
5 gal min · 1.5" adult · Peaceful
Chili Rasbora
Boraras brigittae
5 gal min · 0.8" adult · Peaceful
Florida Flagfish
Jordanella floridae
15 gal min · 2.5" adult · Semi-aggressive
Neon Rasbora
Sundadanio axelrodi
10 gal min · 1.5" adult · Peaceful
Threadfin Rainbowfish
Iriatherina werneri
10 gal min · 1.5" adult · Peaceful
Argentine Pearlfish
Austrolebias bellottii
10 gal min · 1.5" adult · Semi-aggressive
Banner Lyretail
Aphyosemion calliurum
10 gal min · 1.5" adult · Semi-aggressive
Betta Coccina
Betta coccina
5 gal min · 1.8" adult · Semi-aggressive
Black Bar Endler
Poecilia wingei
5 gal min · 1.2" adult · Peaceful
Blackfin Pearlfish
Austrolebias nigripinnis
10 gal min · 1.5" adult · Semi-aggressive
Blue Gularis Killifish
Fundulopanchax sjoestedti
20 gal min · 4" adult · Semi-aggressive
Blue Panchax
Aplocheilus panchax
15 gal min · 3" adult · Peaceful
Bluefin Notho
Nothobranchius rachovii
10 gal min · 2.5" adult · Semi-aggressive
Cape Lopez Lyretail
Aphyosemion australe
10 gal min · 2.5" adult · Semi-aggressive
Cuban Rivulus
Rivulus cylindraceus
5 gal min · 2.2" adult · Peaceful
Eggers' Notho
Nothobranchius eggersi
10 gal min · 1.5" adult · Semi-aggressive
Gardneri Killifish
Fundulopanchax gardneri
10 gal min · 2.5" adult · Semi-aggressive
Gold Medaka
Oryzias latipes
10 gal min · 1.5" adult · Peaceful
Hikari Medaka
Oryzias latipes
10 gal min · 1.5" adult · Peaceful
Ivantsoff's Blue Eye
Pseudomugil ivantsoffi
10 gal min · 1.5" adult · Peaceful
Kilombero Notho
Nothobranchius kilomberoensis
5 gal min · 1.5" adult · Semi-aggressive
Korthaus's Notho
Nothobranchius korthausae
10 gal min · 1.6" adult · Semi-aggressive
Planning this tank?
Run the whole stock list through the calculator — it checks bioload and schooling numbers, not just pairings.