The color of carbon monoxide tuna just looks too red, like a cherry popsickle. REALLY, REALLY fresh tuna looks identical or nearly identical. But tuna almost immediately starts to brown out a bit so anything you see that is cherry red has most likely been treated. Too bad the government won't force the food distributors to label this stuff so we could at least know the difference before we bite into some mealy, old tasteless flesh.
Couple of links on the practice:
http://www.nytimes.com/2004/10/06/dinin ... &position=
My previous point that the sushi chef makes a difference may be validated by the strong feelings, mine included, that Edo Monona Drive is better than Edo Park St. I'm assuming they are related and probably share the same sources and, if so, the chef makes the difference in the sushi.
I fled Wasabi after the CO tuna discussions and also because they had changed the rice recipe which made it chewy. Edo Monona Drive is too far to ride on my bicycle so I most often went to Edo Park St, it was the best alternative at the time. But I do enjoy the view and will chance Wasabi again some day soon.
I only ate at Ginza downtown once, the sushi was fine but the place deserted (which is probably why they closed recently.)