I tend to use darker misos myself (traditionally made kinds wherever possible), so I thought that 'aka dashi' was just miso soup made with the red (aka) variety of miso, hence the 'stronger' taste.

Is it your experience that sushi shops usually serve this kind of miso soup? And if so, is it limited to sushi shops in a certain price range?

I know that konacha (a strong tasting green tea made from the powder/leavings of sencha production) is the typical brew of the sushi-ya. However, I hadn't experienced/noticed that red miso was usual for making the soup. But then I don't go to many kaiten sushi places.

Can you expound? I'm rather curious for your view on this.