I'd say yes and they love koi ponds. Here in FL, it's kinda "cool" to have a koi pond. A woman in my neighborhood has one (3' x 6'). She told me that for several nights in a row she had seen a snake near the pond and that her fish were disappearing, and she had hired a "reptile pest controller" for $300 who came out and placed mothballs around the pond to scare away what he identified as a "cottonmouth viper". She came to me in tears a few days later. The mothballs killed off the rest of the koi and the snake was still there. I went right over and found a Florida Banded Water snake coiled up near the pond, picked it up and relocated it to my property.

Thanks, dbd. There used to be 4 goldfish in my tiny pond. The snake ate 3 of them :( A friend is going to share some her goldfish.
Glad that you rescued the Florida banded water snake.
Mothballs should be taken off the market.

Why dont you cover it with chicken wire

Sad story. You can't say "Cottonmouth," without me thinking of this: https://www.youtube.com/watch?v=TiuGcBYdAPA

Yes, it is a Yellow-bellied Watersnake (N. erythrogaster).