Yes the magnet is flat and the tank is curved but when you stack a whole bunch of acrylic cleaning pads on the inside magnet they follow the curve of the tank, the magnets are very strong so they clean very very well, they are actually hard to move because they are so strong.

yes it is because of the cylindrical tube that the tanks are so expensive, each tube comes out of a huge tool mold thats about 12" long, they are cast cell acrylic, and very expensive. I woyuld guess that the high cost is a result of trying to recover monies fromthe very very expensive mold that are used to make the tube.