How does the stocking calculator work?

Each species has a bioload value (waste load per fish). We add the bioload of every fish you select and compare it to your tank size; ~100% means fully stocked. We also check filter turnover, schooling minimums, minimum tank size and temperament.

Is the “1 inch of fish per gallon” rule accurate?

No. It ignores adult size, body mass, waste output and swimming space. AquaGauge uses a per-species bioload model instead.

What stocking percentage is safe?

Aim to stay at or below ~85–100%. Under 85% gives comfortable headroom; over 100% risks ammonia spikes unless filtration and water changes are excellent.

How much filter flow (GPH) do I need?

A common target is about 4× your tank volume per hour — e.g. ~40 GPH for a 10-gallon tank. Heavily stocked tanks benefit from more.

Aquarium Stocking Calculator

Add your tank size and the fish you want — AquaGauge shows live stocking % and filtration %, and flags overstocking, aggression, schooling and minimum-tank-size problems. It uses a per-species bioload model, not the inaccurate “1 inch per gallon” rule.

Tank size (US gallons)

Filter flow (GPH)

Add fish

Qty

Add fish below to see your stocking level

stocked

Stocking level

of target

Filtration

Stocking — under 85% comfortable · 85–100% full · over 100% overstocked

Show the math

How this calculator works

Every species carries a bioload — a unit of biological waste load per adult fish. We sum the bioload of all your fish and divide by your tank volume (in gallons) to get the stocking %. Filtration % compares your filter’s GPH to a ~4× turnover target. It then checks each fish against its minimum tank size, schooling minimum, temperament and temperature range. This replaces the flawed inch-per-gallon rule. Full model on our methodology page.

Species data used

Curated starter set (23 common freshwater species). Bioload and ranges are tuned against community norms; we are expanding the database.

Species	Adult size	Min group	Min tank	Temperament	Temp °F
Neon tetra Paracheirodon innesi	1.5″	6+	10 gal	peaceful	70–81
Ember tetra Hyphessobrycon amandae	0.8″	6+	10 gal	peaceful	73–84
Cardinal tetra Paracheirodon axelrodi	1.2″	6+	15 gal	peaceful	73–81
Harlequin rasbora Trigonostigma heteromorpha	1.8″	6+	10 gal	peaceful	72–81
Guppy Poecilia reticulata	2″	3+	10 gal	peaceful	72–82
Endler's livebearer Poecilia wingei	1.4″	3+	10 gal	peaceful	72–82
Platy Xiphophorus maculatus	2.5″	3+	10 gal	peaceful	70–82
Molly Poecilia sphenops	4″	3+	20 gal	peaceful	72–82
Zebra danio Danio rerio	2″	6+	10 gal	semi-aggressive	64–77
White cloud minnow Tanichthys albonubes	1.5″	6+	10 gal	peaceful	60–72
Corydoras catfish Corydoras sp.	2.5″	6+	20 gal	peaceful	72–80
Pygmy corydoras Corydoras pygmaeus	1″	6+	10 gal	peaceful	72–79
Otocinclus Otocinclus sp.	1.5″	6+	20 gal	peaceful	72–79
Kuhli loach Pangio kuhlii	3.5″	5+	20 gal	peaceful	73–86
Dwarf gourami Trichogaster lalius	3.5″	—	10 gal	semi-aggressive	72–82
Tiger barb Puntigrus tetrazona	2.8″	6+	20 gal	semi-aggressive	74–82
Serpae tetra Hyphessobrycon eques	1.6″	6+	15 gal	semi-aggressive	72–79
Betta (male) Betta splendens	2.5″	—	5 gal	aggressive	76–82
Angelfish Pterophyllum scalare	6″	—	29 gal	semi-aggressive	76–84
Goldfish (fancy) Carassius auratus	8″	—	30 gal	peaceful	65–72
Cherry shrimp Neocaridina davidi	0.6″	6+	5 gal	peaceful	65–80
Nerite snail Neritina sp.	1″	—	5 gal	peaceful	65–85
Mystery snail Pomacea bridgesii	2″	—	5 gal	peaceful	68–82

FAQ

How does the stocking calculator work?: Each species has a bioload value (waste load per fish). We add the bioload of every fish you select and compare it to your tank size; ~100% means fully stocked. We also check filter turnover, schooling minimums, minimum tank size and temperament.
Is the “1 inch of fish per gallon” rule accurate?: No. It ignores adult size, body mass, waste output and swimming space. AquaGauge uses a per-species bioload model instead.
What stocking percentage is safe?: Aim to stay at or below ~85–100%. Under 85% gives comfortable headroom; over 100% risks ammonia spikes unless filtration and water changes are excellent.
How much filter flow (GPH) do I need?: A common target is about 4× your tank volume per hour — e.g. ~40 GPH for a 10-gallon tank. Heavily stocked tanks benefit from more.