Usually yellow 'stains' are mustard algae -- but that's easy to tell. Just brush the spots; if they brush away easily, you have mustard algae.

What you've used:
+ Surchlor + (sodium hypochlorite 12.5%) => bleach. Walmart bleach is 8.25%, and fresher.

+ Black Algaecide (dimethylbenzyl ammonium chloride 49.8% , methybenzyl ammonium chloride 2% and 48% other) => foamy algaecide; should never be used.

+ 3" chlorinating tablets (93% trichloro-s triazipetrione, 3.5% zinc sulfate monohydrate, and 2.9% other) => slightly diluted trichlor

+ chlorine stabilizer (trihydroxy s-triazine) => cyanuric acid or stabilizer

+ alkalinity plus (sodium hydrogen carbonate) => baking soda (AKA sodium bicarbonate, sodium acid carbonate)

+ PH plus (sodium carbonate) => washing soda (AKA soda ash)

+ Super Mineral Eliminator- 28 oz. (contains citric acid and hydroxyethane diphosphonic acid) => citric acid + HEDP. Citric acid should NEVER be used; ascorbic acid (vitamin C) and HEDP, but ONLY if dealing with a specific metal problem. NEVER use it 'just in case'.

+ 60% nonfoaming algaecide (poly( oxyethylene dimethylimino) ethylene dichloride 60% other 40%) => Polyquat; we often recommend it for a variety of purposes (it's an excellent clarifier), but it's not effective against mustard algae.


The really key factor is your CYA level (reported CYA = 91 ppm). That's a test strip reading, so it's not very accurate, but it is likely that your CYA level is above 60 ppm. You'll have to get a K2006 test kit to find out.

Assuming the 'yellow' brushes away, confirming mustard algae, do these things:

=> Read the Best Guess page, linked in my signature, so you can understand what's happening.

=> Order a K2006 kit, so you can find out what your pool levels really are. (test kit page linked in my signature)

=> Purchase an OTO/phenol red test kit (yellow / red drops) locally. Walmart is fine. (Get the 6-way HTH kit if they have it. This is a trimmed version of the Taylor kit, but it has a CYA test.) OTO allows you to test higher values of chlorine, than any other method, except the DPD-FAS method on the K2006.

=> Purchase 12+ gallons of PLAIN Walmart 8.25% bleach, and began dosing nightly with 4 gallons.

=> Test before dosing; once the OTO test result begins to have an orange tint, skip the dose.

=> Brush the pool every other day, AFTER adding chlorine.



. . . Tell us what you find out.