Pond Lights

I've been keeping the pond lights (two 20 watts) on at night hoping to keep the
water temperature from getting too cold. Here in the Sacramento Valley it's
been getting into the 30's lately. But I'm wondering if this is blinding the
fish to potential predators at night and possibly attracting predators, too.
Unless three of them are constantly hiding (could be) there's three less than
there used to be. Oh...the bond light are submerged. No exterior lights,
either.