Seachem ParaGuard Review Guide: Broad-Spectrum Parasite
Seachem ParaGuard occupies an unusual niche in fish medicine cabinets — it is one of the few broad-spectrum aldehyde-based treatments still licensed for planted tanks and shrimp-adjacent systems. This Seachem ParaGuard review guide looks at what the 250 ml bottle actually does well, where its reputation overtakes its real performance, and how to dose it safely in a Singapore hospital setup. The notes below come from our bench at Gensou Aquascaping in 5 Everton Park, where we have run ParaGuard through everything from stubborn ich on Amazon tetras to opportunistic fungal flare-ups after HDB power outages.
The Active Chemistry
ParaGuard is a malachite-green-free blend of aldehydes, proprietary surfactants and buffers. The active fraction is primarily a stabilised glutaraldehyde-related compound that oxidises on contact with organic parasites, fungi and Gram-negative bacteria. Because it breaks down within 18 to 24 hours, dosing must be repeated daily for the full course rather than left to accumulate.
What It Treats Well
The product genuinely shines against external protozoans — Ichthyophthirius, Chilodonella, Trichodina and mild velvet respond within four to six days at full dose. It also manages saprolegnia fungus on damaged tissue when paired with methylene blue dips. Our parasite identification guide helps match the pathogen to the right tool; guessing wastes the critical first 48 hours.
Where It Falls Short
ParaGuard is weak against established internal parasites, heavy Aeromonas infections and late-stage columnaris. If the fish has ulcerating red sores or breathing through open gills, you need something targeted like KanaPlex or Furan-2 instead. Treat ParaGuard as a first-line external-parasite tool, not a universal cure.
Dosing in Singapore Hospital Tanks
Standard dose is 5 ml per 40 litres once daily for up to 14 days, with a 25 percent water change before redosing. In our tropical 28 to 30 degree ambient, the aldehydes oxidise faster than in temperate climates, so sticking precisely to the daily schedule matters. Set up a bare 40 to 60 litre hospital tub using our hospital tank setup guide, add a cycled sponge filter, and match temperature to the display within one degree before transferring fish.
Plant and Shrimp Safety
Seachem markets ParaGuard as plant-safe, and at the listed dose that largely holds true for hardy stems and crypts. Sensitive carpets like glossostigma and dwarf hairgrass will show melt within three days at full dose. Shrimp tolerate half-dose reasonably well but stop moulting properly, so never medicate a dedicated shrimp tank — move fish out instead. Our plant-safe medication guide lists tolerated species.
Combining ParaGuard With Other Medications
ParaGuard layers reasonably well with aquarium salt at 1 to 2 grams per litre and with short methylene blue dips in a separate container. Do not combine it with formalin, malachite green, or other aldehyde-based products — the stacking stress kills fish faster than the pathogen would. Never mix with hydrogen peroxide dips either.
Filtration and Carbon Interaction
Activated carbon and Purigen strip ParaGuard within hours, so remove both from the hospital filter before dosing. A simple sponge filter with no chemical media is ideal. Keep the UV sterilizer off too; it photolyses the aldehydes and wastes the dose. After the final treatment day, run fresh carbon for 48 hours to clear residuals before returning fish to the display.
Availability and Price Locally
The 250 ml bottle runs $22 to $28 at Iwarna, Polyart and C328, with the 500 ml often better value at around $38. Authorised Shopee listings occasionally dip to $20 with free shipping. Check the lot code and expiry — old stock that has sat in warm warehouses loses potency, and the liquid should be perfectly clear with no cloudiness or sediment.
Tropical Climate Considerations
HDB flat temperatures during haze season or extended power cuts can swing hospital tanks by three or four degrees overnight. ParaGuard’s efficacy drops sharply below 24 degrees and its breakdown accelerates above 30, so a small adjustable heater set to 26 degrees keeps the chemistry predictable. SP Group outages longer than four hours warrant a battery-operated air pump on standby to protect medicated fish.
Verdict
Seachem ParaGuard is a sensible first-choice broad-spectrum external treatment for Singapore freshwater keepers who want a plant-tolerant tool. It will not replace targeted antibiotics for bacterial ulcers, and it cannot reach internal parasites. Keep a bottle alongside your quarantine medication kit, treat it as the front line for external protozoans, and respect the daily redose rhythm and it will serve you well across five years of hospital-tank runs.
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emilynakatani
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