Fish Medication Dosage Calculator
Pick a medication, enter your actual water volume, and get the label-accurate dose — no more guessing with capfuls and teaspoons.
Calculate medication dose
⚠️ Read this before medicating
This calculator is a dosing aid, not a diagnosis tool. Doses shown are taken directly from the manufacturers' published labels and are provided for reference only. Product formulas change — always read your own bottle's label and follow it over anything on this page. For serious, spreading, or undiagnosed illness, consult an aquatic veterinarian.
Label doses used by this calculator
- Seachem ParaGuard — 5 mL (1 capful) per 10 US gallons, repeated daily. Treats external parasites (ich, velvet), fungus and fin rot. Remove invertebrates and chemical filtration first.
- Seachem KanaPlex — 1 level measure (included scoop) per 5 gallons, every 48 hours, maximum 3 doses. Kanamycin-based antibiotic for bacterial/fungal infections (dropsy, popeye, fin rot).
- Seachem MetroPlex — 1–2 measures per 10 gallons, every 48 hours, up to 3 weeks. Metronidazole-based; treats internal parasites and protozoan infections.
- Kordon Methylene Blue (2.303%) — 1 teaspoon per 10 gallons (produces 3 ppm), for fungus on fish and eggs and some external parasites. Stains silicone permanently; use a bare hospital tank.
Medication safety basics
- Dose by actual water volume, not tank size — subtract substrate, rocks and decor. Overdosing is the most common medication mistake.
- Remove chemical filtration (activated carbon, Purigen) and turn off UV sterilizers — they strip medication from the water.
- Increase aeration during treatment; many medications reduce dissolved oxygen.
- Never mix medications unless the labels say it is safe — combinations can be toxic.
- When in doubt, treat in a hospital/quarantine tank rather than the display tank, especially with invertebrates or live plants present.
Frequently asked questions
How much ParaGuard per gallon?
5 mL per 10 gallons (0.5 mL per gallon), repeated daily as long as fish show no stress.
How often do you dose KanaPlex?
One level measure per 5 gallons, every 48 hours, for a maximum of 3 doses.
Should I remove my filter when medicating?
Remove chemical media (carbon, Purigen) and switch off UV — keep mechanical and biological filtration running.
Can I use Methylene Blue in a reef tank?
No. It is not reef safe, stains silicone, and is absorbed by rock and wood. Use a bare hospital tank.