How the site is funded
FinsAndFigures is free to use. To pay for it, some pages may contain affiliate links and, in future, advertising. An affiliate link is an ordinary link to a shop: if you buy something after following it, the shop may pay us a small commission. You pay the same price either way.
As an Amazon Associate we may earn from qualifying purchases.
What affiliate links never change
- The calculations. A result is the same whether or not anything is for sale. No formula is adjusted to favour a bigger or dearer product.
- What we recommend. We describe what to look for in a product (the wattage, the flow, the features that matter) based on the calculation and on established fishkeeping practice. Where we name specific products, we choose them on their merits, and brands cannot pay to be included.
- What we say against a product. If a common product type is a poor choice, we say so.
How links are marked
Pages that contain affiliate links say so near the links. Advertisements, when shown, are labelled as advertising and kept apart from the calculators.
Accuracy and corrections
Every calculator is tested against published examples before release, and each page shows the date it was last reviewed. If you find a mistake, email hello@finsandfigures.com. We correct errors promptly and note significant changes on the page.
A note on advice
The tools and guides here are general information for hobbyists. They are not veterinary advice, and the glass and weight calculators are not structural engineering advice. For a sick animal, see an aquatic vet; for a large custom tank or a doubtful floor, consult a qualified professional.
Last updated 14 November 2026.