Yellow algae

[Wanda.M]

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 do

 

[woodyp]

Welcome to the forum. First of all we're going to ask for a full set of chemical testing from an accurate kit. How are you testing?

 

[JamesW]

Pictures?

It might be iron stains.

Drop a vitamin C tablet on a spot.