Inch-per-gallon is goldfish-bowl advice. Count waste, not inches.

A 10-inch oscar is not ten neon tetras. Adult size and mess class decide whether the tank stays cycled.

Points: small (≤2") = 1, medium (2–5") = 3, large (5–10") = 8, XL (10"+) = 14. On a normal setup, capacity equals the gallon count. A heavy-stock setup allows 0.6 points per gallon.

Use it in 10 minutes. Add the adult sizes you actually want, not the juveniles at the store. Stay under the tank's point cap. Heater watts below are this calculator for 68°F to 78°F. Filter ratings are the normal level: 5 turnovers, then a 20% step.

Tank recipes

Tank	Capacity (pts)	Heater, 68°F to 78°F	Filter rating, normal
10 gal	10	50 W	60
20 gal	20	100 W	120
29 gal	29	150 W	175
55 gal	55	250 W	330
75 gal	75	300 W	450

Same calculator results as the aquarium-stocking.com homepage. Planning estimates, not a published standard.

Ten small fish in a 20-gallon normal setup are 10 points, 50% of capacity, comfortable. A fish sold for a 20 that outgrows it does not belong on that list.

Comment keyword: FISH — that's the word we ask for on X/LinkedIn. We DM this page.

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Sources & Standards

Bioload points, watts per gallon, and filter turnover on these pages are planning estimates for a cycled freshwater tank. They are not a published standard.

Frequently asked questions

Is this calculator free?

Yes — free to use, no signup, no email required.

How accurate is the estimate?

Estimates follow industry-standard sizing rules and common safety margins. Always confirm with a licensed professional for final sizing.

Can I use this on mobile?

Yes — the page is fully responsive and works on phones, tablets, and desktop.

Where does the math come from?

Formulas are shown inline on the result panel so you can verify each step yourself.