Oil and fuel additives

I am not saying it won't happen but due to the lack of light present in an enclosed fuel tank, it is unlikely for algae to bloom. The word "Algae" has become a catch all word for contaminants we all see in our diesel. The most common of all is bacteria and other contaminants.
https://www.bellperformance.com/bell-performs-blog/recognizing-diesel-fuel-algae