Is this mustard algae?


TFP Expert
LifeTime Supporter
Jun 12, 2009
NW Ohio
Doesn't look like it, and mustard algae would disperse with a light brushing. Looks and sounds like some kind of staining, possibly iron judging by the color or perhaps organic.

Do you have either chlorine tablets and/or vitamin C pills you could hold against the step stains for a few seconds to see how they react?


LifeTime Supporter
May 5, 2012
Johnson City, TN
I was about to say I realized it wasn't mustard algae because it is in a location of direct sunlight (as is most of my pool, which I guess bodes well for mustard algae prevention). I took a stiffer brush to the stuff on the step, and it starts to come off, so it is clearly some sort of stain. No chlorine tabs available, but Vitamin C tablet did nothing, really, although it was difficult to tell because the tablet is mostly sugar. Any tips on stain removal?