There's a million of 'em!

I tried Mosquito Fish in my Koi pond a few years ago, but they didn't make
it through the winter, which is fast approaching, even here in Southern
California.

Is there something I can put on/in the water that will kill them without
harming the lotuses and water chestnuts nor make them toxic to eat?

Thanks.

--
Nick. Support severely wounded and disabled Veterans and their families!
I've known US vets who served as far back as the Spanish American War. They
are all my heroes! Thank a Veteran and Support Our Troops. You are not
forgotten. Thanks ! ! ~Semper Fi~