We had our first pool installed last year and my family has been following the pool store's recommendations for chemicals. This year, I got tired of the over-chlorination and bought a TF-100 kit. Around the same time, we noticed a lot of brown "dirt" on the bottom of the pool. My family talked to the pool store who insists its mustard algae. I think its just dirt, since I was able to vacuum the pool floor clean and it took a couple days for it to reappear (settling, I assume).
They want to dump a special algae treatment in, I want to avoid adding more chemicals if unnecessary. It's a fiberglass pool. Tested chemicals on the 29th, FC was 31 and CYA was 80. Tested it again yesterday and FC was down to 22, CYA remained at 80.