Observed arrival · 2026-09-28

FishMaths: aquarium math, without the spreadsheet

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Editorial interest 72/100 Selection signal · not a rating of the site

A free set of browser-based calculators for aquarium volume, substrate, heaters, stocking, water changes, dosing, and CO2.

Landing page captured for the 2026-09-28 issue.

For: Aquarium keepers sizing tanks and managing water care
Worth noticing: The site warns that a nominal 20-gallon tank may hold closer to 17 gallons after gravel, rocks, and the gap at the top.

Field notes

The volume tool is described for rectangular, cylindrical, and hexagonal tanks, while the reference chart lists dimensions, liters, and weight for tanks from 5 to 125 gallons. Other listed tasks include scaling a product dose to tank size and estimating a water change to reach a nitrate target. The page characterizes its results as estimates and advises following product labels and testing water.

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