How To Train Your Fish

As I don't wish anyone to form the wrong opinion of the person involved here, so I'll let you guess the identity of the Hertfordshire born non-Norfolk person...
Had a 'phone call telling me about the way the new fish were jumping in and out of the water near a newly installed filter.
"They do that all the time" I said, "you can even train them to do it"
"Really"? replied the non- Norfolk person
"Oh yes. You can even buy a special jump for them. Start with just the one jump and add more, the fish will soon be using them for exercise."
"Where can I buy them"?
"Any good pond retailer. They're called Fish Hurdles and they're light weight jumps built on polystyrene so they float"
I was quite pleased I came up with the idea on the spot, and as far as I know the non-Norfolk person (NNP) is still looking for Fish Hurdles to train her Koi.