Green algae turning black

[TinyWood]

This green hair algae has turned black some of it had lost color and turned white I figured that was winning the battle but this black seemingly over night is unsettling

 

[taricha]

Looks like your dying GHA fueled a cyano mat. That's the dark red/ purple covering the gha.
What were you doing against the gha that you said was working?

 

[TinyWood]

2 gallon water changes every other day in a 7g tank

 

[taricha]

Ok. If the gha is receding, then don't worry about the cyano, except you can vacuum it out during water changes.
When dying GHA is gone, cyano may fade away too.

 

[TinyWood]

Will this hurt my urchin he got close stopped and turned around could be pure coincidence but just want to ask

 

[taricha]

Urchins are pretty dang tough. It might choose to avoid the patch, but it certainly won't be harmed by the cyano.