Mustard algae, help!

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S

SU373

Member
Aug 4, 2022
5
New Jersey
Hi,

We are new pool owners as we recently bought a house with a salt water pool and are struggling with maintenance as we learn abt pool care. We recently found this site and are hoping you can help.

We definitely have a case of mustard algae and are trying to get rid of it. We started by brushing and vacuuming the whole pool as best we could and sanitizing everything pool related. We then used 6lb of dichlor 4 in 1 shock on Monday and have been brushing any spots that pop up. However it seems that we haven’t eliminated the algae as it keeps coming back in the same spot (see attached photo, looks green in pic but is actually mustard colored).

Pool store suggested Poly60 to just outright kill all the algae so we can start our maintenance from scratch, would this help?

Our current test results are:
Ph 7.5
TA 100
FC 13.5
CC 0.5
CYA 70
CH 400

Not sure what to do next, what do you suggest?
 

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Welcome to the forum!
You need to follow the SLAM Process. To do that, you need a proper test kit. I suggest the TF-100 / TFPRO or Taylor K2006C. A proper test kit is needed to get the accurate water chemistry results needed to follow the TFP protocols.

Poly60 does not kill algae. It is used when winterizing a pool for some extended algae protection. It is useless with elevated FC in the pool water. The chlorine will consume it, rapidly.

While you are waiting on your test kit, add 5 ppm FC worth of liquid chlorine / plain bleach to your pool each evening with the pump running. This will replenish the FC lost each day to the sun and also inhibit any algae in the water from growing further.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool
 
Thank you for the quick reply!

We actually have the TFPRO test kit and that’s where the results above come from does this change anything?

Seems that the info in my signature isn’t coming up but we have a 20k gallon vinyl pool with an attached spa and a 48 sqft DE filter, and a Hayward TCELL925 SWG. The pool spends a large portion of the day in direct sunlight. The water is currently clear and the only indicator of the problem is the returning algae in the spot in the middle of the pool where the pool starts getting deeper. Weirdly, this area is in direct sunlight most of the day but the algae keeps coming back.

I read through the SLAM process and it seems that CYA at a level of 70 requires FC levels that may not be safe for the pool. How to handle this? Do we have to drain significant amounts of water to lower the level before starting?

And since we already shocked the pool are the other results (aside from CYA and FC) accurate?

Additionally, the page on mustard algae recommends that after the regular slam process, we should do a mustard algae SLAM process with a higher level of FC to ensure it’s eliminated. Is this correct or do we use the higher level for the initial SLAM?

Another question - my kids are desperate to use the pool. Is it safe for them to use it during the SLAM process and will we have to resanitize everything they use in the pool due to the risk of mustard algae contamination?
 
Great! You have what you need.
Raise your FC to SLAM level for your 70 ppm CYA. That is 28 ppm. No harm, you can even swim if you can see the bottom of the pool.
Read the SLAM Process.

How have you determined that you have mustard algae? Do NOT go to Mustard Algae SLAM level FC until you fully complete the initial SLAM process.
 
mknauss said:
Great! You have what you need.
Raise your FC to SLAM level for your 70 ppm CYA. That is 28 ppm. No harm, you can even swim if you can see the bottom of the pool.
Read the SLAM Process.

How have you determined that you have mustard algae? Do NOT go to Mustard Algae SLAM level FC until you fully complete the initial SLAM process.
Click to expand...

In the beginning we didn’t know what it was it and it was growing up sides of the pool and everywhere in the pool so we brushed and vacuumed and added 2lb of pool shock and it came back (see pic attached, got significantly worse a few days after the pic) After doing some research we realized that it’s probably mustard algae (since it’s easily brushed off but keeps coming back)and that’s when we did the process I detailed above.

Regarding the mustard slam level after, the required FC level is 40.5 for CYA of 70 is that too high? Also is it safe to use the pool at this level of chlorine as well?

Unfortunately, we won’t be around to maintain the SLAM on Saturday, should we wait until next week to start the process and is there anything we need to do until then to prevent it from getting worse?

It’s good to hear that we can use the pool if it’s clear (which it is) but will we have issues reintroducing the algae from the pool toys? And just to confirm, such high levels of chlorine won’t cause irritation? (Apologies for all the newbie questions, all this is very overwhelming and I’m worried I’m getting confused)
 
I suspect it is regular algae. Mustard is quite rare.

Start the SLAM now. Maintain the FC at SLAM level as often as possible.
If you decide to do the Mustard FC level after the SLAM, do not use the pool while the FC is above normal SLAM levels.
 
Thanks!

Since I’m new to this I retested the CYA again just to make sure and now I’m at 60.

Since the test is very subjective I’m not sure what level to use for SLAM. Does it matter if the FC is slightly higher than recommended for your CYA level?
 
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