Growth in window frames

[ian w]

I have a sort of moss type of stuff grows in my window frames outside when l leave the boat for2 monhs Is there a chemical l can leave on the windows runners to stop this

 

[captcrunch]

Following

 

[cww]

Same, it happens in the galley windows and it's a total PITA to clean, you can't get your hand or anything in there easily. Would love to know how to stop that.

 

[SEVEN]

I used 2 coats of bleach and rinsed thoroughly. Hasn’t returned in 7 years.