Frustrated and don't understand

[Deb_B]

My numbers are as follows

FC - 8
CC - 0
CYA - 35-40ish
TA - 110
CH - 220

I raise my FC to 10 each evening because it is so darn hot here (outside Galveston) and I am not here to dose mid day if FC falls below 4.

Day before yesterday I noticed yellow dust on the bottom of the pool. Vacuumed, brushed and raised my FC to 10 again. Water started looking a little green.

Same situation the next day. Just lightly green.

This am around 11am this morning FC was 9.5 with no CC but my ph was sky high. Added acid. Level only dropped to 8 today but my water is even more green and there is MORE yellow dust on the bottom.

How can I have algae with these numbers?

[chem geek]

Welcome to The PoolForum! :)

It sounds like you have yellow/mustard algae. Does the algae grow mostly on the shady side of the pool?

How are you getting your pool water chemistry numbers? What test kit (brand/model; drop-based or test strips) are you using or are these numbers from a pool store?

Tell us more about the type of pool you have. In-ground vs. above-ground. Plaster, vinyl, fiberglass pool surface. Size in gallons. Number of returns and whether you have a floor drain or pop-ups, etc. Size of pump. Type of filter (sand, cartridge, DE).

[Deb_B]

Intex 16 x 48 vinyl liner 6700gal AGP installed 7/2013
Intex 2500 gph cartridge pump/filter (Unicel Filter)
BBB only - Still learning.

My kit is a mix right now. Started with HTH 6 and have added FAS/DPD and CYA test from tftestkits.net

I am still passing the over night test and still have no cc or .5. Never over.

My cya is accurate as I have had myself, my husband and my daughter all run the test. 35-40ish

I figured it had to be mustard algae. Nothing else made sense. Last night I dosed the pool to 24 ppm per the PoolCalc and it was still in the 20s at 3:00pm today. .

The only off thing is my PH skyrocketed above 8.2 tonight. Should I treat even though the test may not be accurate?

[chem geek]

Don't worry about the pH while you are shocking. Just note for the future that you want to lower your pH to around 7.2 or even a bit lower before you shock to high levels such as yellow/mustard algae levels. For yellow/mustard algae, you need to get behind light niches and under removable ladders and need to put poles and other equipment into the pool water while it is shocking. This algae likes to hang out in shady areas and it will come back if you don't completely eradicate it.

[Watermom]

If you test pH when the chlorine is high, then you will get a falsely high reading.

Once you get this cleared up, you may want to bump your CYA higher to help you make it through the day without your chlorine dropping too low. Maybe try around 50. If you still have trouble, may try 60 or wo.