Help With Mustard Algae

[monovendros]

I’ve been having a bit of trouble with getting rid of mustard algae on our pool. I did verify that it’s organic (I rubbed a chlorine puck on an area and it cleared up, but the total area is too big to continue doing that everywhere). It has cleared up on the sides of the pool that get sun but persists in the shaded areas.

It showed up when I drained the pool to lower my CYA - the line of algae is where the water level was before refilling.

Attached is the log. Testing is done with a TF-Pro kit.

Current numbers:
==========================================
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Build Type: Plaster
Volume: 25000 gallons
Chemistry: Liquid Chlorine
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Latest Test Result Summary:
FC: 22.0 (3 hours ago)
CC: 0.0 (3 days ago)
pH: 7.2 (5 days ago)
TA: 100 (5 days ago)
CH: 475 (5 days ago)
CYA: 45 (5 days ago)
TEMPERATURE: 84° (16 days ago)
CSI: -0.12 (3 hours ago)
==========================================


I started the SLAM on Aug 30 trying to keep my FC at 18. TFP says to complete the SLAM and then raise to MA SLAM for 24 hours, but the walls aren’t clearing up at all so I don’t think I’ll ever hit the third criterion of not having anything on the walls.

I have brushed every day (sometimes 2x a day) with a stainless steel brush with no luck.

At this point I have dumped 35 gallons of liquid chlorine in the pool over the last 30 days with no effect and have been running my pump continuously for over two weeks.

Does anyone else have any other ideas to try? Thanks in advance!

 

[Donldson]

It sounds like you're describing organic staining. Mustard algae is a chlorine resistant algae that can brushed away easily, staining is a splotch on the finish that doesn't brush away but fades or clears when rubbed with a chlorine tablet.

 

[JamesW]

Looks more like metals to me.

Probably iron and maybe some copper.

 

[monovendros]

Looks more like metals to me.

Probably iron and maybe some copper.

I rubbed a chlorine puck in one spot and a vitamin c tablet in another - the spot with the puck disappeared but not the spot with the tablet.

My test kit doesn’t test for metals but the Leslie’s test came back with 0 phosphates copper and iron (but not sure about accuracy for those tests)

 

[JamesW]

You only get widespread organic staining if the water is really nasty for a long time.

If the staining happened with clear water, it is probably metal.

The water tests for metals can show 0 if most of the metal is in the stains and not in the water.

 

[monovendros]

You only get widespread organic staining if the water is really nasty for a long time.

If the staining happened with clear water, it is probably metal.

The water tests for metals can show 0 if most of the metal is in the stains and not in the water.

Makes sense! Would metal stains disappear with chlorine pucks being rubbed on them?

 

[JamesW]

To me, it looks like iron.

Try a Jack's Stain Id kit.

 

[monovendros]

To me, it looks like iron.

Try a Jack's Stain Id kit.

Thanks! Would iron clear up by rubbing chlorine on it?

 

[JamesW]

Would iron clear up by rubbing chlorine on it?

Possibly, because trichlor is very acidic.