red algae

[waterbear]

Water chemistry is good, plenty of chlorine, and algaecide, pH is 7.2 and total alkalinity is in line.
Anybody seen anything like it?

"red algae" is actually bacterial (cyanobacter) AND you would not have it if your 'water chemistry is good'. It occurs when the water chemistry is off. As Watermon said, please post a full set of test results.