Cat-safe algae control??

I have a small pond that loves algae. But I don't! Though I have a UV
filter, there's still plenty of string algae. What I'm wondering is
whether any of the algae control products -- many list copper as the
active ingredient -- can be used when my pond also serves as a drinking
bowl for my 6 cats.

And, please, don't waste my time telling me to get rid of the cats or
cover the pond with a net to keep them from drinking, etc etc

The cats stay and perhaps so will the alage unless I can find a product
safe for their ingestion.

Thanks for the help.

ps offlist cc's to would be appreciated