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Mustard algae is chlorine-resistant. Standard shocks won't kill it.
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Mustard Algae Won't Die With
Mustard Algae Won't Die With
Standard Shocks.
It is one of the most chlorine-resistant algae strains. This guide walks you through the full chemical and physical treatment process to eliminate it permanently.
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The Complete Protocol
How to Eliminate Mustard Algae For Good
Mustard algae survives standard shocks. You need aggressive chlorine levels plus physical removal. Follow these steps exactly. Each step includes the right product for the job.
1Correct Chemistry & Brush
Test and balance pH to 7.2-7.6 first. Mustard algae forms a waxy protective layer. Use a stainless steel brush for concrete pools or a nylon brush for fibreglass and vinyl pools to break it open so chemicals can penetrate.
7-in-1 Test Strips
Instant ResultsLab Accuracy
$24.99
2Vacuum to Waste + Clarifier
Vacuum loose algae directly to waste. Do not send it through the filter. For cartridge filters, add a clarifier to consolidate fine particles for easier capture without clogging your cartridge.
Clarifier 1L
Crystal ClearFilter Safe
$29.99
3Heavy Shock (Liquid Chlorine)
Add 10 to 15 litres of liquid sodium hypochlorite for an average pool. Liquid chlorine is preferred because it adds no cyanuric acid (CYA). High CYA reduces chlorine effectiveness significantly. If your CYA is above 50 ppm, partially drain and refill before starting.
Liquid Chlorine
No CYAFast Acting
Available at Bunnings or pool shops
4Run Filter ยท Scrub ยท Vacuum
Run pump continuously for 24 hours. Scrub all surfaces again. Algae lifts after shock. Let particles settle for 2 to 4 hours, then vacuum to waste. While the system runs, test phosphates. High levels feed mustard algae and cause regrowth.
Phosphate Remover 1L
Starves Algae1L treats 50,000L
$49.99
5Add Algaecide (Metal-Free)
Once no visible algae remains, add a non-staining, metal-free formula algaecide. This is the best choice for mustard algae prevention because it creates a residual barrier without adding copper or other metals that can stain pool surfaces. It won't foam, won't stain, and won't interfere with chlorine.
Algaecide 1L
Non-StainingMetal-FreeNo Foam
$39.99Buy 2 Get 1 FREE
6Sanitise All Accessories
Submerge brushes, vacuum heads, scoops, hoses, and pool toys in highly chlorinated water for several hours. Rinse thoroughly afterwards. For metal stains on accessories or pool surfaces, use Metal Remover to prevent discolouration.
Metal Remover 1L
Prevents StainingEquipment Safe
$34.99
7Maintain High Chlorine
Keep chlorine at superchlorinated levels of 10 to 15 ppm for 2 to 3 days. Brush all surfaces daily. High chlorine raises pH. Use pH Down to keep it in the 7.2 to 7.6 range for maximum effectiveness.
pH Down 1kg
Precise ControlDry Acid
$19.99
Why Mustard Algae Keeps Coming Back: High stabiliser (CYA) reducing chlorine effectiveness, insufficient chlorine levels, poor circulation in dead spots, not cleaning accessories, dirty filter media, treatment stopped too early, or phosphates providing ongoing nutrients. A non-staining, metal-free algaecide used monthly prevents recurrence without adding metals that can stain.
Optional Final Step
Finish With Oxi Shock
After the main treatment is complete and chlorine levels have returned to normal, Oxi Shock provides the perfect finishing touch. It oxidises remaining organic waste and removes chloramines for a cleaner, more comfortable pool.
Water TechniX Oxi Shock 500g
Non-Chlorine Formula
Swim in 15 Minutes
Removes Chloramines
Stops Itchy Skin
Australian Made
Oxi Shock is a powerful, chlorine-free oxidiser. It breaks down dead algae cells, body oils, sunscreen residues, and other organic waste that accumulated during the mustard algae outbreak. Unlike chlorine shock, you can swim just 15 minutes after adding it.
$24.99
Dosage: 1 x 500g tub treats up to 40,000 litres. Add directly to the pool with the pump running.
When to use Oxi Shock: Wait until chlorine levels have dropped to 2-4 ppm after the main treatment. Then add Oxi Shock to clear any remaining cloudiness and eliminate the "chlorine smell" caused by chloramines.
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