Hairy Cyano like algae toxic?

[paddyob]

So I'm doing maintenance. I hsve what my research says is a type of Cyano. Thought it was hair algae, but it's bubbly and removes easily from the rocks.

Five minutes after cleaning most out, my tang starts going white and my orange back wrasse keels over. Moved her to a QT but she died.

Not having good luck.

So is this shït toxic? How the **** do I remove it? Will red slime remover work on all cyanos?

I did a 15g water change and all in the tank looks fine today. But the Cyano.

Help!