Aquarium Medication Dosing Calculator
Calculate exact medication or supplement doses for your aquarium.
Enter tank volume and dose rate per gallon to get the precise treatment amount.
Overdosing aquarium medications kills fish. Underdosing fails to treat the disease and risks creating drug-resistant strains. Getting the volume right is not optional.
Dose = net water volume × dose rate per gallon
The tricky part is net water volume. Your tank listed volume (10 gal, 55 gal) is the gross capacity. Substrate, rocks, decorations, and equipment displace water — typically 10–20% of tank volume. A “55-gallon” tank often holds 45–50 gallons of actual water. For powerful medications with a narrow therapeutic window (copper treatments, for example), use the conservative estimate.
Remove activated carbon before treating. Carbon absorbs medication within hours and renders the treatment useless. This is the most common reason a first round of treatment fails.
Some medications reduce oxygen. If the label suggests it, run an airstone during treatment, especially at higher temperatures when dissolved oxygen drops naturally.
Half-dose caution for invertebrates: many medications are toxic to shrimp, snails, and crabs even at doses that are therapeutic for fish. If your display tank has inverts, research the specific medication first. Moving fish to a separate hospital tank for treatment is often safer than medicating the main tank.
Quarantine tanks prevent this problem entirely. A 10-gallon bare-bottom tank with a sponge filter is inexpensive and allows you to treat new fish before they enter your display tank, and sick fish without exposing the rest of the tank to medication stress.
After treatment, run fresh activated carbon for 24–48 hours to remove medication residue before it affects your biological filter.