Is GHA toxic to fish?

[glb]

A few days ago I brushed a lot of gha off my rocks and the next morning I noticed one of my clownfish died. I added Prime to the tank after scrubbing off the algae just in case. Could I have caused an ammonia spike or is the algae itself toxic to fish if it's in the water column?

 

[Reefing Madness]

No, not last time I checked. Some will actually eat it, some will not.

 

[glb]

If you brush it off the rocks though, does it die and degrade the water?