Dirt Stain On New Plaster; How Do I Remove It?

[TexasPool128]

We have a 2 month old pool. Somehow 2 dirt balls sat on the plaster for a few days (I was gone for work and family was supposed to be brushing 2 times a day). I’ve tried aggressively brushing/scrubbing them but have gotten nowhere. They’re on one of the steps in about 1.5’ of water and about 1/4” in diameter. Pool guy that did the start-up said to put MA in a mustard bottle and squirt it directly on the spots then scrub but I don’t know if this is a good idea.
How do I remove these small stains?
Thanks!

 

[mknauss]

His idea might work but is pretty aggressive.

Try vitamin C tablets. Might be iron. If that has no effect, then your chlorine will eventually fade it.

 

[sktn77a]

The muriatic acid will certainly get rid of the stain but, as stated above, is very aggressive on that area of the plaster. Chlorine will be just as effective on an organic stain.