Are you peering into the blue depths of your swimming pool and wondering why that patch of dirt on the bottom or pool walls isn’t being sucked up by your pool cleaner? There’s a good chance that it’s not dirt at all, rather, it’s a rather bothersome form of algae known as mustard algae. 

Well, that’s just not okay, because we take a great deal of pride in maintaining a super-clean pool with all the right chemicals, so what’s the issue here?

Mustard algae?

Mustard algae are – well – algae, similar to the black and green algae which we’ve previously discussed.

The main difference, besides its yellowish colour, is its rather stubborn resistance to chlorine. 

Bioguard says, “Mustard algae is a chlorine-resistant form of green algae that often resembles dirt or sand on bottom or sides of the pool. 

“It contains compounds that act as a defence mechanism against the oxidation efforts of sanitizers, helping it survive even in highly chlorinated conditions. This factor can even create a large chlorine demand in certain situations. Mustard algae can be brushed away very easily but return quickly.”

Because of its dogged determination to remain in your swimming pool, the permanent removal of mustard algae requires a somewhat merciless approach. It can live happily in any part of your swimming pool, including your filter and pool toys, and can also lurk outside your pool on pool cleaning equipment and your swimming costumes. 

Getting rid of mustard algae will need some determination and, we’re afraid to say, a little hard work.

Scrubbing your swimming pool walls down and vacuuming it thoroughly is your first step to dislodge any mustard algae. Follow this with pool shock for a good, solid sanitising and let your pool pump run for a full 24 hours. In the meantime, be sure to wash down anything that goes into the water with a bleach solution and pop those swimming costumes in for a warm and soapy washing machine cycle.

You may well have to repeat the scrub, vacuum, and shock approach a couple more times to ensure the complete removal of mustard algae. It’s also worth chatting to the Pool Spa team who can advise you on which treatments are likely to offer the best result in your battle against this tiny, yellow enemy.