a new and troublesome problem has come to the pool. RED ALGAE!!!

My in ground gunite pool has defects in the old plaster like shallow craters. I have had black algae in these craters before but a little algaecide and shock with a vigorous scrubbing with a stainless wire brush quickly took care of it. the red stuff not so much.

It is also on the little plastic in the pool, ladder steps and skimmers. Water chemistry is good, plenty of chlorine, and algaecide, pH is 7.2 and total alkalinity is in line. On the plaster it is only in the "craters" where the surface is the roughest. The water is crystal clear and can see over 40 ft. underwater with a mask.

Anybody seen anything like it?