There are a lot of differing opinions on that. Some people think you should change out more, but I think changing just 20 percent is less stressful on the aquarium and fish. Once you get used to the regimen, it's pretty easy.
There is something about a home aquarium which sets my teeth on edge the moment I see it. Why anyone would want to live with a small container of stagnant water populated by a half-dead guppy is beyond me.
The country's newest aquarium, opened in November, bills itself as the largest in the world, holding more than 100,000 animals representing 500 species. It is the first in the USA to display whale sharks, the largest fish in the world.
And when you come back to Japan next summer, let's have that date or whatever you want to call it. We can go to the zoo or the botanical garden or the aquarium, and then we'll have the most politically correct and scrumptious omelets we can find.