New member
Jan 2, 2020
Sydney, NSW, Straya
Hello all,

new to TFP. haven’t done an OCLT yet (looking to get fas dpd test kit)

could anyone confirm (by looks) is this is algae ? I think I’m in denial.

There is a backstory including my SWG being out of whack for couple months and pool turning slightly green, I did the stainless steel brush of walls/floor, then vacuum to waste, shock and some algaecide (this was around 2-3 months ago), it did recover (and was blue!) but there has always been this residue build up which I thought is sand due to a lot of stormy windy conditions and pool is in high leaf area.

Haven't managed to vacuum to waste fully all the residue, due to water level dropping too fast, so not clear if it's just sand spreading back or new algae growth/bloom?

Currently pool looks clear, I did add some clarifier a few weeks back (believe works like floc) so wondering if it's possible it's just sand/inorganic material that have settled on floor (but then walls have it too)

Yellow algae? Possible I initially had both green algae (as the water had turned slightly green before shock treatment) and yellow algae which is persisting due to cl resistance?

Pool shop had one look at photo and said "looks like black algae" and sold me shock/cl powder sodium dichloro.

Other readings are generally ok and around the levels below. pH was high added dry acid few days ago.

pH - 7.2-7.8
TH - 250
Cl - 3
TA - 180
CYA - 30 (maybe)

Salt - 5200ppm

I think my pool is painted/concrete.

The readings are mostly by test strips / dpd kit. CYA on the strip doesnt seem accurate but a month ago pool store gave me reading of 40 (both early and mid Nov)

If it's def yellow algae I want to treat it accordingly.


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New member
Jan 2, 2020
Sydney, NSW, Straya
Update - how it looks after a quick vacuum to waste.
The residue is not slimy but feels silky smooth fine substance. When touched it just dispersed into the water. There was a layer of it across large surface areas on pool floor and walls. There's also clumpy collections on pool floor.


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Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Welcome to the forum!
The material sounds like dead algae -- so you have an active algae bloom. Once you get your proper test kit run the Overnight Chlorine Loss Test. Do the complete suite of tests as you need accurate data which you cannot get from your current testing regimen.
In the mean time -- read SLAM Process
I suggest you read ABC's of Pool Water Chemistry.


Mod Squad
LifeTime Supporter
Jul 10, 2012
Tallahassee, FL
You need a full test kit. Those guess strips may be VERY wrong on the CYA. You really need to know the real CYA level in order to do the SLAM your pool needs.

So far you have kept ahead of a full algae bloom but after a while the algae will end up winning and taking over the whole pool. It will be even harder to beat it. See if you can get a test kit from here: Kits – Clear Choice Labs They have awesome customer service!

Look at the posts above for the link to how to do a SLAM. Have you found a good source for liquid chlorine in your area? You are going to need quite a bit of it to get the pretty pool clean and sparkling again!



New member
Jan 2, 2020
Sydney, NSW, Straya
Thanks all, and for the links.
Will be getting the kits from clear choice labs :).

Yes liquid Cl in 15L tubs (hardware store, will check dates). Sodium hypochlorite 125G/L avail which I guess is the 12% commonly referred to. Used before.

For now ill have to start the SLAM a little blind without reliable CYA as the kit gets shipped out. I'll try and get a CYA reading from a store anyway. the dpd kit should give me ball park FC readings over the next few days so I can use that to monitor. CYA more than likely dropped as it was 30-40 around 6 weeks back, will use that as a reference.
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