Phyllis and Jim wrote:
That seems a sensible worry. Ours is plumbed in and has not been an
issus in more than a decade. It's volume is small enopugh that it
does not harm the pond...3-4000 gal with constant circulation.

Jim

Same with mine. Although in the AZ heat the plastic bottle finally
sprung a leak and I had to change it this year after 20 yrs. If you
look at your pond more than twice a day, it should be no problem. If
you are worried over a long vacation, they are easy to shut off. Saves
a ton of hassle with hoses and stuff.

Chip