We have a 20' X 10' koi pond with 7 Koi in Washington State. We just put crayfish into the pond based on a recommendation. Will they harm the Koi here during winter hibernation? Do you have a different suggestion to keep the pond clean?

Hi Don,

Crayfish are mini-predators, and will catch and eat small fish if they can. In a liner pond, they won't help much, and probably won't survive the winter. Nowhere to hide or hibernate. They are part of a natural pond's ecology, but need the dirt bottom and the vegetation.

If you want a clean bottom and have bare liner, you need a bottom drain system. Algae is controlled with a Plecostemus, but you've got to be able to catch the little bugger in the fall, 'cause they're trops, and won't tolerate water below about 60 F.

If your pond has a rock or pebble bottom, you'll have sludge. Period.

(Answer courtesy Bob Passovoy)