I believe StarTron enzyme treatment contains enzymes which digest large particles of asphalt and other deposits over time. I'm not aware of it being a biocide, ie, killing fungus/bacteria. I think you can look it up online.

I have a bottle of it in my trunk, and have been using it for over a year. I haven't checked to see if the pieces of black gunk in the bottom of the tank are gone yet. I haven't had any problems with pieces breaking off and clogging the primary filter, but that's just my experience.

BioBor is an example of a biocide.

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Marshall Welch
Seattle, WA
1982 300D-T