Algae in my hydraulic fluid

[TMGT]

Is the fluid you're using a bio fluid or supposed to be "less toxic" if leaked on a field? That's about the only time I've seen algae grow like that is with bio fluids.
Hopefully it was just caused by the high water content which might be fixed now.
I believe some algae can can live and grow at elevated temps so I wouldn't think usage would kill it off necessarily.