Though this product doesn't actually say it's for use with Koi Carp, in my ignorance I thought it was the correct Elodea for all Koi. My Koi shredded them in about an hour flat, leaving the remnents floating on the surface. Perhaps they are for small aquariums/fish only.
Anyhow, the next time I bought Elodea is was definely some Elodea Crispa, which is Koi proof (or at least for me it was!). Perhaps my Koi are a bit rowdy, but from another review I've seen they're obviously not the only ones that destroy these plants. Unfortunately I didn't see the other review until it was too late.
It should be made clearer in the advert what this variety of Elodea is, and what it's actually for.