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Spotted an error, want a calculator we don't have yet, or have a question? Email us.

Helpful things to include: which calculator, the numbers you entered, the result you expected, and where your expected value comes from (a test kit, a manufacturer chart or a textbook).

We read every message but can't promise a reply to all of them. We don't give veterinary advice. For sick fish, contact an aquatic veterinarian or a reputable local fish store.