He designs some kind of scientific equipment, or at least he did - not sure if he's full time with his aquarium business now or not. I forget what his aquarium business is called, I'll get back to you on that one - but they build massive concrete reef tanks for very rich people, and they build equipment for very large reef tanks - pretty cool stuff, but his skimmers are very expensive.
Of course, with a bit of time and ingenuity you could build a large protein skimmer yourself for around $1,500 - one with the same specifications as Mr. Wann's would run you at least $10,000.