KickJ9
I've had them in my garden so the bird thing makes a lot of sense.
There's plenty of snails in my pond. Granted I do not have koi so I am not reccomending this by any means

but as my fish seemed to slow down on feeding that's when i noticed the abundance of snails. I have a soft spongy brush (like for washing bottles) to scrape the sides of the pond to jar loose the snails. My fish gobble them up and many will attach themselves to the sponge as well. Those attached to plants are a total pain and I have found no other way but handpicking. Maybe a very fine screened net etc. to catch them after jarring?
I read of baiting snails by using certain foods like lettuce or algae wafers - possibly place inside a nylon?, wait til darkness sets and remove (move in for the kill

), in which the snails will be attached to. This sounds like a good idea actually. I would remove all plants at that time and clean them.
Someone needs to invent birthcontrol for these pesky hermaphrodites
Good Luck ~ Pam