How to Get Rid of Mustard Algae in Your PoolUpdated a month ago
Mustard algae (yellow or brownish-green) is stubborn, chlorine-resistant, and loves shady spots in pools. Here’s how to nuke it for good and keep your water crystal clear.
1. Identify Mustard Algae
Appearance: Dusty yellow patches on walls, corners, or behind ladders.
Texture: Brushes away easily but returns quickly.
Test: Rub a chlorine tablet on the spot—if it lightens, it’s algae.
2. Super-Chlorinate (Shock) the Pool
Balance water first: Test with a reliable pool test kit.
pH: 7.2–7.4 (low pH boosts chlorine’s effectiveness).
Alkalinity: 80–120 ppm.
Triple-shock the pool:
Use calcium hypochlorite or liquid chlorine. DO NOT USE STABILISED CHLORINE
Dose 30–40 ppm chlorine (≈1kg of shock per 10,000L).
Brush aggressively: Scrub walls, floors, and hidden areas (algae clings to biofilm).
3. Use a Mustard Algaecide
Water TechniX Algaecide: Designed for algae that thrive in Australian pools
Copper-based algaecides: Effective but can stain surfaces (use with caution).
Run the pump 24–48 hours to circulate chemicals.
4. Clean Everything
Filters: Backwash sand/DE filters or soak cartridges in filter cleaner.
Equipment: Scrub poles, brushes, and toys with chlorine solution.
Swimwear: Wash in hot water to kill spores.
5. Prevent Reinfestation
Maintain chlorine: Never let it drop below 3 ppm for 1–2 weeks post-treatment.
Brush weekly: Disrupt algae’s grip on surfaces.
Use preventative algaecide: Add a weekly dose during peak season.
Reduce phosphates: Test and use phosphate remover.
When to Call a Pro
Algae returns repeatedly (indicates deeper plumbing contamination).
Stains or damage from copper-based treatments.
Need Algae-Killing Gear?
Browse our Pool Chemical Collection for heavy-duty treatments and phosphate removers. Pair with a stainless steel brush or algae brush for stubborn spots.
Final Tip: Mustard algae is sneaky—stay vigilant! Cover the pool after treatment to block spores from blowing back in.