Could be. Here's one thing in Oregon, not sure if it's what I remember, but I don't think so because it appears to be a going concern: http://www.oregonlive.com/foodday/index.ssf/2011/10/real_was...

"Mountain streambeds are the plant's natural habitat. Though some Japanese wasabi is cultivated in soil, the highest quality product is water-grown, with plants sprouting from gravel-laced terraces through which streams are diverted."

Still sounds tricky compared to a lot of stuff.

Makes it sound perfect for aquaponics.