What is this "algae" on my mixing brute?

[Philly Reefer]

I mixed this 3 weeks ago. I never seen this before. I always rinse the brute when its empty. Salt is TM Pro. I can wipe them off. It doesn't seem to be floating around.
This brute is in the garage with no light. Last few weeks temps have been up around 80F.

What is this? Is this safe to use? Can I just siphon those off and use the saltwater still?

 

[lapin]

Im sure its safe to use.
As for what it is, i duno.
Maybe some impurity in the salt (new bucket)?
Algae needs light to grow.