I would really appreciate your advice on the following matter. I have a koi pond of 15m x 5 m with about 65000 liter capacity. Have about 40 koi with sizes from 15 to 45cm. I would love to get a pair of mute or black swans. Would you advise this or give any advice? The pond does have plants in and a proper filtration system.

Does the feces of the swans create a health risk for the koi?

Thanks for your help
Ronald