Seachem PolyGuard

Hospital tank use only.Remove all invertebrates before dosing. PolyGuard contains malachite green, which is lethal to shrimp, snails, and corals and can tint the water during treatment.

Seachem PolyGuardis one of Seachem’s strongest broad-spectrum medications, treating bacterial, fungal, and external parasitic infections in freshwater and marine fish. Because it combines several active ingredients, it is the medication to reach for when you are unsure what disease you are facing, when a fish is fighting more than one infection, or when a single-target treatment has not worked. Browse our full range of fish medications and the rest of the Seachem lineup.

What PolyGuard Treats

• External bacterial infections, fin and tail rot
• Body and mouth fungus, cottony growths
• External parasites such as flukes and other skin and gill parasites
• Mixed or unidentified infections where a single medication is not enough
• Stubborn cases that did not respond to a gentler, single-target treatment

Why Hobbyists Reach for It

• Broad spectrum.Combines antibacterial, antifungal, and antiparasitic agents in one treatment.
• Freshwater and marine.Safe to use in both when invertebrates are removed.
• Best for the unknown.Ideal when symptoms point to more than one problem or the cause is unclear.
• Easy to remove.Lifts out with activated carbon and does not linger in substrate or filter media.

How to Use

Use 1 measure (the included scoop) for every 40 litres (about 10 US gallons). Repeat the dose every 72 hours for a maximum of 2 weeks, which is up to 5 doses over the full course. Treat in a dedicated hospital or quarantine tank with all invertebrates removed. After the final dose, perform a partial water change and run fresh activated carbon to clear any remaining medication and tint.

Choose Your Size

	PolyGuard 10 g	PolyGuard 100 g
Net weight	10 g powder	100 g powder
Coverage	several full courses for a small tank	about 10x the 10 g for repeat or large-system use
Best for	one or two tanks, occasional treatment	fish rooms, larger tanks, frequent quarantine work

Specifications

Brand	Seachem
Type	Broad-spectrum medication (antibacterial, antifungal, antiparasitic)
Active ingredients	Sulfathiazole, malachite green, nitrofurantoin, nitrofural, quinacrine
Form	Powder (measuring scoop included)
Water type	Freshwater & Marine
Treats	Bacterial, fungal, and external parasitic infections, including mixed cases
Dose	1 measure per 40 L (about 10 gal), every 72 hours, up to 2 weeks
Invertebrates	Remove all inverts before dosing; extremely sensitive. Hospital tank only.
Water tint	Contains malachite green; may tint water during treatment
Carbon removable	Yes
Sizes	10 g, 100 g

Recommended Pairings

• Seachem SulfaPlex for milder, single-target bacterial or fungal infections.
• Seachem KanaPlex for gram-negative bacterial infections and septicemia.
• Seachem MetroPlex for internal and protozoan infections.
• Water care and conditioners to support fish during and after treatment.

FAQ

Does PolyGuard work in both freshwater and marine tanks?
Yes. It is labeled for use in freshwater or marine aquaria, as long as all invertebrates are removed first.

Will it stain my tank?
PolyGuard contains malachite green, which can tint the water and may lightly stain silicone. Treat in a hospital tank and run activated carbon after the course to clear the color.

Is it safe for shrimp, snails, and corals?
No. Invertebrates are extremely sensitive and must be removed before dosing. Always treat affected fish in a separate hospital tank.

When should I use PolyGuard instead of a gentler medication?
Reach for PolyGuard when the disease is severe, when more than one infection is present, when the cause is unknown, or when a single-target treatment has not worked. For milder cases, a gentler option such as SulfaPlex may be enough.