Best Fish for a 40 Gallon Tank

The forty-gallon breeder is the aquascaper's favourite footprint: shallow, wide, and stable. It comfortably houses medium cichlids, large schools, and species that need swimming length rather than height.

96 species · ordered by how many Shoal & Stem keepers have them · every card links to a full care guide

Otocinclus

Otocinclus vittatus

medium

10 gal min · 1.5" adult · Peaceful

Pygmy Corydoras

Corydoras pygmaeus

easy

10 gal min · 1" adult · Peaceful

Celestial Pearl Danio

Danio margaritatus

easy

10 gal min · 1" adult · Peaceful

Guppy

Poecilia reticulata

easy

10 gal min · 2" adult · Peaceful

Halfmoon Betta

Betta splendens 'Halfmoon'

easy

5 gal min · 2.5" adult · Semi-aggressive

Ember Tetra

Hyphessobrycon amandae

easy

10 gal min · 0.8" adult · Peaceful

Julii Corydoras

Corydoras julii

easy

15 gal min · 2.5" adult · Peaceful

Neon Tetra

Paracheirodon innesi

easy

10 gal min · 1.5" adult · Peaceful

Panda Corydoras

Corydoras panda

easy

15 gal min · 2" adult · Peaceful

Fancy Guppy

Poecilia reticulata

easy

10 gal min · 2" adult · Peaceful

Honey Gourami

Trichogaster chuna

easy

10 gal min · 2" adult · Peaceful

Cherry Barb

Puntius titteya

easy

15 gal min · 2" adult · Peaceful

Kuhli Loach

Pangio kuhlii

easy

20 gal min · 4" adult · Peaceful

Black Neon Tetra

Hyphessobrycon herbertaxelrodi

easy

10 gal min · 1.5" adult · Peaceful

Endler's Livebearer

Poecilia wingei

easy

10 gal min · 1.5" adult · Peaceful

Harlequin Rasbora

Trigonostigma heteromorpha

easy

10 gal min · 2" adult · Peaceful

Peaceful Betta

Betta imbellis

medium

10 gal min · 2.5" adult · Peaceful

Platy

Xiphophorus maculatus

easy

10 gal min · 2.5" adult · Peaceful

Bristlenose Pleco

Ancistrus sp.

easy

20 gal min · 5" adult · Peaceful

Bronze Corydoras

Corydoras aeneus

easy

20 gal min · 2.75" adult · Peaceful

Peppered Corydoras

Corydoras paleatus

easy

20 gal min · 2.75" adult · Peaceful

Plakat Betta

Betta splendens 'Plakat'

easy

5 gal min · 2.5" adult · Semi-aggressive

White Cloud Mountain Minnow

Tanichthys albonubes

easy

10 gal min · 1.5" adult · Peaceful

Albino Corydoras

Corydoras aeneus

easy

15 gal min · 2.5" adult · Peaceful

Clown Pleco

Panaque maccus

easy

20 gal min · 3.5" adult · Peaceful

False Julii Corydoras

Corydoras trilineatus

easy

15 gal min · 2.5" adult · Peaceful

Betta

Betta splendens

easy

5 gal min · 2.5" adult · Semi-aggressive

Bolivian Ram

Mikrogeophagus altispinosus

easy

20 gal min · 3.5" adult · Peaceful

Cardinal Tetra

Paracheirodon axelrodi

easy

15 gal min · 2" adult · Peaceful

Clown Killifish

Epiplatys annulatus

medium

5 gal min · 1.5" adult · Peaceful

Emerald Dwarf Rasbora

Danio erythromicron

medium

10 gal min · 1" adult · Peaceful

Galaxy Koi Betta

Betta splendens 'Galaxy Koi'

easy

5 gal min · 2.5" adult · Semi-aggressive

Green Neon Tetra

Paracheirodon simulans

medium

10 gal min · 1" adult · Peaceful

Hillstream Loach

Sewellia lineolata

medium

20 gal min · 2.5" adult · Peaceful

Koi Angelfish

Pterophyllum scalare

medium

30 gal min · 6" adult · Semi-aggressive

Marble Angelfish

Pterophyllum scalare

medium

30 gal min · 6" adult · Semi-aggressive

Powder Blue Dwarf Gourami

Trichogaster lalius

medium

15 gal min · 3.5" adult · Semi-aggressive

Rummy Nose Tetra

Hemigrammus rhodostomus

medium

15 gal min · 2" adult · Peaceful

Salt & Pepper Corydoras

Corydoras habrosus

easy

10 gal min · 1.5" adult · Peaceful

Siamese Algae Eater

Crossocheilus oblongus

easy

30 gal min · 6" adult · Semi-aggressive

Swordtail

Xiphophorus hellerii

easy

20 gal min · 4" adult · Peaceful

Zebra Danio

Danio rerio

easy

10 gal min · 2" adult · Peaceful

Albino Bristlenose Pleco

Ancistrus sp.

easy

20 gal min · 5" adult · Peaceful

Chili Rasbora

Boraras brigittae

medium

5 gal min · 0.8" adult · Peaceful

Crowntail Betta

Betta splendens 'Crowntail'

easy

5 gal min · 2.5" adult · Semi-aggressive

Delta Betta

Betta splendens

easy

5 gal min · 3" adult · Semi-aggressive

German Blue Ram

Mikrogeophagus ramirezi

hard

20 gal min · 3" adult · Peaceful

Green Corydoras

Corydoras aeneus

easy

15 gal min · 2.5" adult · Peaceful

Kerri Tetra

Inpaichthys kerri

easy

10 gal min · 1.2" adult · Peaceful

Molly

Poecilia sphenops

easy

15 gal min · 3" adult · Peaceful

Pearl Gourami

Trichopodus leerii

easy

30 gal min · 5" adult · Peaceful

Tiger Barb

Puntigrus tetrazona

easy

20 gal min · 3" adult · Semi-aggressive

Veiltail Betta

Betta splendens

easy

5 gal min · 3" adult · Semi-aggressive

Apistogramma Borellii

Apistogramma borellii

easy

20 gal min · 3" adult · Semi-aggressive

Blood Parrot Cichlid

Amphilophus citrinellus × Vieja melanurus

medium

30 gal min · 8" adult · Semi-aggressive

Cobra Guppy

Poecilia reticulata

easy

10 gal min · 2" adult · Peaceful

Dalmatian Molly

Poecilia sphenops

easy

20 gal min · 3" adult · Peaceful

Double Tail Betta

Betta splendens 'Double Tail'

medium

5 gal min · 2.5" adult · Semi-aggressive

Dwarf Gourami

Trichogaster lalius

easy

15 gal min · 3.5" adult · Semi-aggressive

Emerald Corydoras

Brochis splendens

easy

20 gal min · 3" adult · Peaceful

Glowlight Tetra

Hemigrammus erythrozonus

easy

10 gal min · 1.5" adult · Peaceful

Gold Barb

Barbodes semifasciolatus

easy

20 gal min · 3" adult · Peaceful

Gold Dust Molly

Poecilia sphenops

easy

20 gal min · 3" adult · Peaceful

Lambchop Rasbora

Trigonostigma espei

easy

10 gal min · 1.75" adult · Peaceful

Lemon Tetra

Hyphessobrycon pulchripinnis

easy

10 gal min · 1.5" adult · Peaceful

Red Rainbowfish

Glossolepis incisus

easy

40 gal min · 5" adult · Peaceful

Red Swordtail

Xiphophorus hellerii

easy

20 gal min · 4.5" adult · Peaceful

Rubber Lip Pleco

Chaetostoma milesi

easy

25 gal min · 5" adult · Peaceful

Silvertip Tetra

Hasemania nana

easy

10 gal min · 1.5" adult · Semi-aggressive

Sparkling Gourami

Trichopsis pumila

easy

10 gal min · 1.5" adult · Peaceful

Sterbai Corydoras

Corydoras sterbai

easy

20 gal min · 2.5" adult · Peaceful

Sunset Honey Gourami

Trichogaster chuna

easy

10 gal min · 2" adult · Peaceful

Venezuelan Corydoras

Corydoras venezuelanus

easy

15 gal min · 2.5" adult · Peaceful

X-Ray Tetra

Pristella maxillaris

easy

15 gal min · 1.75" adult · Peaceful

Banded Rainbowfish

Melanotaenia trifasciata

easy

40 gal min · 5" adult · Peaceful

Black Kuhli Loach

Pangio oblonga

easy

20 gal min · 4" adult · Peaceful

Black Molly

Poecilia sphenops

easy

20 gal min · 3" adult · Peaceful

Black Moor Goldfish

Carassius auratus

easy

20 gal min · 7" adult · Peaceful

Black Phantom Tetra

Megalamphodus megalopterus

easy

15 gal min · 1.75" adult · Peaceful

Bloodfin Tetra

Aphyocharax anisitsi

easy

15 gal min · 2" adult · Peaceful

Boesemani Rainbowfish

Melanotaenia boesemani

easy

30 gal min · 4.5" adult · Peaceful

Bumblebee Goby

Brachygobius xanthomelas

medium

10 gal min · 1.5" adult · Semi-aggressive

Comet Goldfish

Carassius auratus

easy

40 gal min · 12" adult · Peaceful

Dwarf Chain Loach

Ambastaia sidthimunki

medium

15 gal min · 2" adult · Peaceful

Dwarf Neon Rainbowfish

Melanotaenia praecox

easy

15 gal min · 2.5" adult · Peaceful

Eastern Rainbowfish

Melanotaenia splendida

easy

30 gal min · 4.5" adult · Peaceful

Electric Blue Acara

Andinoacara pulcher hybrid

easy

30 gal min · 6" adult · Semi-aggressive

Elephant Ear Betta

Betta splendens 'Dumbo'

easy

5 gal min · 2.5" adult · Semi-aggressive

Emerald Eye Rasbora

Brevibora dorsiocellata

easy

10 gal min · 1.5" adult · Peaceful

Emperor Tetra

Nematobrycon palmeri

easy

15 gal min · 2" adult · Peaceful

Exclamation Point Rasbora

Boraras urophthalmoides

medium

5 gal min · 0.8" adult · Peaceful

Florida Flagfish

Jordanella floridae

easy

15 gal min · 2.5" adult · Semi-aggressive

Forktail Rainbowfish

Pseudomugil furcatus

easy

10 gal min · 2" adult · Peaceful

Glass Catfish

Kryptopterus vitreolus

medium

30 gal min · 4" adult · Peaceful

GloFish Danio

Danio rerio

easy

10 gal min · 2" adult · Peaceful

GloFish Tetra

Gymnocorymbus ternetzi

easy

15 gal min · 2" adult · Peaceful

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