Fish Stocking Calculator
Enter your tank size and pick your fish. Get a safe stocking recommendation based on biomass, school size, and filtration.
Step 1 — Your tank
Step 2 — Your fish
No fish added yet. Search above to start building your stocking plan.
Stocking plan
20 gal · 75.7 L
Safe range per species
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Species we cover (40)
Every fish in the calculator links to its care guide. Don't see yours? It's freshwater-only for now.
Paracheirodon innesi
Schooling · 1.5" adult
Paracheirodon axelrodi
Schooling · 2" adult
Hemigrammus erythrozonus
Schooling · 1.5" adult
Hyphessobrycon amandae
Schooling · 0.8" adult
Hemigrammus bleheri
Schooling · 2" adult
Gymnocorymbus ternetzi
Schooling · 2.5" adult
Trigonostigma heteromorpha
Schooling · 1.75" adult
Danio margaritatus
Schooling · 1" adult
Danio rerio
Schooling · 2" adult
Tanichthys albonubes
Schooling · 1.5" adult
Puntius titteya
Schooling · 2" adult
Corydoras aeneus
Schooling · 2.5" adult
Otocinclus vittatus
Schooling · 2" adult
Pangio kuhlii
Schooling · 4" adult
Melanotaenia boesemani
Schooling · 4" adult
Pterophyllum scalare
Cichlid · 6" adult
Mikrogeophagus ramirezi
Cichlid · 2.5" adult
Mikrogeophagus altispinosus
Cichlid · 3" adult
Pelvicachromis pulcher
Cichlid · 4" adult
Poecilia reticulata
Livebearer · 2" adult
Xiphophorus maculatus
Livebearer · 2.5" adult
Poecilia sphenops
Livebearer · 4" adult
Xiphophorus hellerii
Livebearer · 5" adult
Poecilia wingei
Livebearer · 1.2" adult
Carassius auratus
High Bioload · 10" adult
Carassius auratus
High Bioload · 8" adult
Hypostomus plecostomus
High Bioload · 20" adult
Ancistrus cirrhosus
High Bioload · 5" adult
Panaqolus maccus
High Bioload · 3.5" adult
Betta splendens
Centerpiece · 3" adult
Trichogaster lalius
Centerpiece · 3.5" adult
Trichogaster chuna
Centerpiece · 2.5" adult
Trichopodus leerii
Centerpiece · 4.5" adult
Epalzeorhynchos frenatum
Centerpiece · 6" adult
Balantiocheilos melanopterus
Centerpiece · 14" adult
Sewellia lineolata
Schooling · 2.5" adult
Neocaridina davidi
Invertebrate · 1.5" adult
Caridina multidentata
Invertebrate · 2" adult
Neritina natalensis
Invertebrate · 1" adult
Pomacea bridgesii
Invertebrate · 2" adult
How this works
We estimate each fish's adult biomass (grams) and weight it by a bioload factor — high-waste fish like goldfish count for more, low-metabolism fish like bettas for less. The total is divided by your tank's liters to get grams per liter (g/L). Planted tanks, heavy filtration, and frequent water changes each buy you a little more capacity.
Read the full methodology arrow_forwardImportant
This is a planning guide, not a guarantee. Adult size and waste output vary by individual, diet, and temperature. Always research each species, add fish gradually, and test your water. For sensitive or valuable stock, consult an experienced aquarist or aquatic veterinarian.