Caring for your roof is one of the most important jobs as part of home maintenance.
And controlling moss in Western Oregon is an on-going challenge.
Here's a description of the chemical control products for roofs:
Yes, some of them can be toxic for aquatic life.
The products work well to prevent moss from growing, but will work better if moss is removed with physical methods first.
Here are the physical methods to control moss:
I hope that this information helps you to make an informed decision about how to manage moss on your roof.
Please let me know if you have any further questions.