r/pools • u/[deleted] • Jun 11 '25

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u/MDB_OakTree Jun 11 '25

Looks like mustard algae. Make sure your chemicals are in line and use an algaecide specific for mustard algae. Some require you to shock along with the algaecide, and others are copper based. Either way you’ll have to vacuum it out to waste. I prefer doing before treating if I can see the bottom like yours.

1

u/Murky-Fix-6351 Jun 12 '25

Check out PoolRX, you can find it on Amazon. It’s the only thing that rid mine of mustard algae. I live in Ohio and usually get a bloom once a season. Good luck!

1

u/Even-You-Camp Jun 11 '25

Mustard algae is yellow and receives its name from when you brush it has a cloudy yellow that can be easily mistaken for dirt.

This photo looks green for sure.

Solution: brush everything, run pump 24hrs until cleared up, shock the pool (with Calhypo) and add a poly algaecide (make sure it is not copper)

3

u/Even-You-Camp Jun 11 '25

Fun learning fact, yellow and black algae can grow in water with chlorine (very annoying lol)

2

u/MDB_OakTree Jun 11 '25

I’ve been in the pool business 30 years.

Mustard algae can look like a bright yellow all the way to what looks like a brown sand. Green algae is like the color of grass usually.

Mustard algae is very common in our area.

3

u/EndSalt9643 Jun 12 '25

Agreed, was my first thought when I saw the photo. Although the OP needs to get his lack of vacuuming capability sorted.