Dead algae?

[Mike921]

I have a dual aquatic life fixture and I had a huge algae breakout. So I treated with API algae fix and it all turned grey. Is that dead? How do I get rid of it? I was thinking about getting blue mystery snails would they be ok with my plants? Any thought or help on how I could get rid of this would be great I've been waiting for my plants to grow more to trim them which seemed to help a little