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Mustard algae keep coming back
- Thread starter Leo_Wood
- Start date
Mark Davis
Member
Mustard algae’s sneaky it hides in spots your brush can’t always reach. Shocking helps short term, but for long-term control I had to clean everything: ladders, pool toys, even the back of the skimmer flap. I also boosted my chlorine to the high end of the range and kept it there for a full week. That finally stopped it from coming back.
John Miller
Member
Same problem here it always came back in the shady corners. I started using a dedicated algaecide for mustard algae once a week and kept brushing every day for a while, even after it looked gone. Also important: wash swimsuits and floats if they’ve been in the pool with algae. I didn’t do that at first, and I think that’s what kept reintroducing it.
Olivia Reed
Member
Ugh, mustard algae is the worst. What finally worked for me was replacing the filter media entirely. I use a sand filter and didn’t realise the sand had been in there for… I don’t even wanna say how long lol. Once I changed it out, it was like night and day.
Also started adjusting my pump schedule so it runs early morning and late afternoon. I used to only run it midday, but I think the algae were thriving when water sat still overnight and right before sunset. Mustard stuff seems to like those low-light hours. been way better since making that change.
Sometimes it’s not just about killing it, it’s making the water way less comfy for it to come back.
Also started adjusting my pump schedule so it runs early morning and late afternoon. I used to only run it midday, but I think the algae were thriving when water sat still overnight and right before sunset. Mustard stuff seems to like those low-light hours. been way better since making that change.
Sometimes it’s not just about killing it, it’s making the water way less comfy for it to come back.
Elara Brooks
New member
Mustard algae is tricky because it loves corners and any shaded spots where circulation is weak. What finally worked for me was a three-step approach: first, I brushed the walls and corners daily, making sure to get under ladders and steps. Second, I ran the pump longer each day, especially in the early morning and late afternoon, so water keeps moving in those dead zones. Third, I used a mustard-specific algaecide for a week, keeping my chlorine at the top of the recommended range the whole time.
Also, I learned to clean anything that touches the water, floats, toys, pool brushes, because even tiny traces of algae can reseed the pool. After doing all that consistently, it hasn’t come back for me.
Also, I learned to clean anything that touches the water, floats, toys, pool brushes, because even tiny traces of algae can reseed the pool. After doing all that consistently, it hasn’t come back for me.
Katherine Morgan
Member
I fought that same battle for a while. What finally broke the cycle was keeping chlorine a little higher than usual for more than just a day or two, plus running the pump longer to push water into those shaded corners. I also washed swimsuits and pool gear outside the pool, turns out the algae was hitching a ride back in. Since then, it hasn’t come back.
Nathan Parker
Member
I fought this longer than I want to admit and the big mistake I made early was treating it like regular green algae. Shock would knock it back, brushing made it disappear for a couple days, then boom, same corners and shady spots again. That’s because mustard algae isn’t really dying, it’s just laying low. Normal chlorine levels don’t scare it much, especially if circulation is weak.
What finally worked was stretching the process out instead of doing one big hit. I brushed those corners every single day for a full week, not just until it looked clean. I raised chlorine to the high end and actually kept it there, not overnight, but for several days straight. At the same time I aimed a return directly at the problem wall because that area barely moved water. Filter pressure stayed normal, but the water in those corners was basically stagnant before.
The long term fix wasn’t just chlorine though. I realized the algae kept having something to eat. My phosphates were high from runoff and lawn stuff, so even after killing it, it had fuel to come back. Using aquadoc phosphate remover was the turning point. Once the food source was gone, the mustard algae stopped rebounding. I also cleaned anything that touched the pool, brush, net, floats, even tossed swimsuits in the wash, because that stuff absolutely reseeds the pool.
Now I don’t keep chlorine cranked all the time. I just make sure circulation hits shady spots and nutrients stay low. Mustard algae is less about one big shock and more about making the pool uncomfortable for it long enough that it can’t regroup. Anyone else notice it always comes back in the exact same corners until circulation and nutrients are fixed?
What finally worked was stretching the process out instead of doing one big hit. I brushed those corners every single day for a full week, not just until it looked clean. I raised chlorine to the high end and actually kept it there, not overnight, but for several days straight. At the same time I aimed a return directly at the problem wall because that area barely moved water. Filter pressure stayed normal, but the water in those corners was basically stagnant before.
The long term fix wasn’t just chlorine though. I realized the algae kept having something to eat. My phosphates were high from runoff and lawn stuff, so even after killing it, it had fuel to come back. Using aquadoc phosphate remover was the turning point. Once the food source was gone, the mustard algae stopped rebounding. I also cleaned anything that touched the pool, brush, net, floats, even tossed swimsuits in the wash, because that stuff absolutely reseeds the pool.
Now I don’t keep chlorine cranked all the time. I just make sure circulation hits shady spots and nutrients stay low. Mustard algae is less about one big shock and more about making the pool uncomfortable for it long enough that it can’t regroup. Anyone else notice it always comes back in the exact same corners until circulation and nutrients are fixed?