HELP, I don’t know if I have mustard algae or sand in my pool and I’ve tried EVERYTHING to kill it if it’s Mustard algae.


New member
Apr 28, 2021
Gadsden, AL
I’ve had “mustard algae” for a year and a half and have literally tried everything in the books to kill it and most things twice. We even changed the sand in our filter to zeolite and the laterals looked fine to us plus the seals and all. I get splotches of sand colored stuff in the bottom of my pool. We vacuum to waste constantly plus have tried everything. I’m almost to the point of honestly thinking it’s sand. When I touch it, it doesn’t feel like sand nor is it slimy. It goes mostly to wherever isn’t getting the most circulation. It turns white when we shock it or use yellow out, black algae killer, algaecide, or whatever it may be that we are using at the time to kill it. I want to put a cloth on my jet to see if anything comes out, but the jet is very powerful and I wouldn’t know how to put something like that on there and it stay. The “algae” does go away easy but, it returns not necessarily in all the same places but, it does get into cracks and other places in my pool. I will attach some photos but, the color isn’t it’s true color in the photos. I am at a loss and I hate not being able to use my pool. It’s only 3 years old. The black specks are big debris and the last photo is it when it’s white. It’s hard to see. Please help, it’s driving me crazy. The pool store doesn’t believe it’s mustard algae and I just had phosphates for the first time just in the last 2 weeks and they are over 2k. We have stuff to get rid of them.


  • 52C92365-327C-42DE-95C0-D370B422525A.jpeg
    270.7 KB · Views: 35
  • 953CF344-D509-4870-9125-BA9AA5D257E7.jpeg
    287.5 KB · Views: 38
  • 6142CA05-3CF4-43C8-A232-89D28354C4C5.jpeg
    164.2 KB · Views: 33

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
Texas, San Antonio/Marion, South-Central Area
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Welcome to TFP! :wave: Well, it may be algae. Mustard Algae (MA) will often find shady areas on the floor and walls. Many are having big pollen issues this year which can mimic MA, but pollen sits on the surface and falls to the floor, not walls. The black spots may be regular algae. Either way, it's best we confirm a few things first before assuming it's Mustard Algae right off the bat:
- Can you post a full set of water test results? That has to be step one.
- Update your signature. See mine as an example. Be sure to include which test kit you use. If it's not a TF-100 or Taylor K-2006C, it really needs to be.
- Tell us how you chlorinate on a daily basis.

We'll start there and build upon your responses to try and help you.

  • Like
Reactions: Wobblerlorri
Thread Status
Hello , This is an inactive thread. Any new postings here are unlikely to be seen or responded to by other members. You will get much more visibility by Starting A New Thread