Seachem PolyGuard – Strong All-in-One Treatment for Unknown Diseases

When you're not sure what it is, treat everything.

Sometimes a fish is clearly sick but the diagnosis isn't obvious — or it's fighting several infections at once — and guessing wrong wastes precious time.

Seachem PolyGuard is one of Seachem's strongest medications: an effective safeguard against prevalent bacterial, fungal, and parasitic diseases. It's the right call when you're unsure what you're treating or a fish has multiple infections. For freshwater or marine aquaria.

PolyGuard reflects the science-driven approach Seachem has taken since it was founded in 1979 in Madison, Georgia. As a chemistry-led company whose products are developed and manufactured in-house by chemists and backed by research, Seachem built PolyGuard as a filter-safe, multi-active formula — it won't harm your biological filtration when used as directed — and it's easily removed with activated carbon once treatment is complete.

1. Ensure the tank is cycled and stable, then remove invertebrates and chemical filtration.
2. Dose 1 measure per 40 L (10 US gallons) every 72 hours, up to 2 weeks.
3. Also useful whenever introducing new fish.

Cover every base at once. Add to cart.

Why Seachem PolyGuard

• Strong, all-in-one coverage: a multi-active formula that safeguards against prevalent bacterial, fungal, and parasitic diseases at once — ideal when the diagnosis is uncertain.
• Filter-safe: won't harm the beneficial bacteria in your biological filtration when used as directed on a cycled, stable tank.
• Easily removed with carbon: lift residual medication with activated carbon (MatrixCarbon) after treating.
• Seachem chemistry: a research-backed blend of sulfathiazole, malachite green, nitrofurantoin, nitrofural, and quinacrine dihydrochloride developed in-house since 1979.

Best For

Use PolyGuard in freshwater or marine fish aquaria when you're unsure what you're treating, when a fish is fighting multiple infections, or whenever introducing new fish. It covers a broad range of bacterial, fungal, and parasitic diseases. Treat only on a fully cycled, stable tank, and remove all invertebrates before dosing — it is not intended for invertebrates or reef systems.

What It Treats

A broad range of bacterial, fungal, and parasitic diseases — a strong, all-in-one option for unknown or multiple infections.

Directions

Before treating: Remove all invertebrates. Turn off UV and ozone filters and remove chemical filtration (MatrixCarbon, Purigen). Make sure the tank is fully cycled and stable — poor water quality is the root cause of most disease.

Dosing: Use 1 measure (included) per every 40 L (10 US gallons). Repeat every 72 hours (every 3 days) for up to 2 weeks or until symptoms disappear. Use whenever introducing new fish.

After treating: Remove with activated carbon (MatrixCarbon).

Active Ingredients

Sulfathiazole (36%), malachite green (1.9%), nitrofurantoin (0.14%), nitrofural (0.14%), quinacrine dihydrochloride (0.27%). Inactive ingredients: excipients (61%).

FAQ

Is PolyGuard safe for invertebrates or reef tanks? No. Remove all invertebrates before dosing; PolyGuard is not intended for invertebrate or reef systems.

How do I remove PolyGuard after treatment? Run activated carbon (MatrixCarbon) in your filter once the course is complete to lift residual medication.

When should I reach for PolyGuard over a targeted medication? Use it when the diagnosis is unclear or a fish has multiple infections at once, and as a safeguard whenever introducing new fish. If you know the specific disease, a targeted Seachem medication may be the better first choice.