Yellow algae stain

[pabrown56]

I have a 24ft pool and the water is so clear and beautiful but the bottom has yellow or what they call mustard algae. It has been scrubbed very hard for days. We have used algaecide 64 oz of it which was more than required. But over a couple days not all at once. But it's not budging. What else can I doFirst spring with

First spring with new pool. I had the same problem, nice clear water but brownish/yellowish stain started a few weeks ago and brushing would not remove it. I put some shock powder (CaHypo) directly on the stain and waited a few minutes and brushed, the stain cleaned up nicely. I shocked the rest of the pool, brushed it, the ran the pump all night. All the staining was removed. I'm still not sure if was algae or organic stain due to springtime bloom from surrounding trees. I'm leaning toward organic stain as algae can usually be brushed off.

 

[Texas Splash]

Welcome to TFP! I would start by performing an Overnight Chlorine Loss Test to ensure you aren't still battling a live algae issue. If you pass the OCLT, then you may need to maintain a slightly elevated FC level (based on your CYA) as noted on the FC/CYA Levels. It may just take some time for the chlorine to break the stains down.