I just tested out the demo, thanks for the link. During the demo the fish stayed by the screen/window the entire time. You know from one corner then to the other side and so on. I wanted to see it swim around the rock or something showing some depth, but never did. The graphics are VERY nice.
I didn't read anything about being able to feed the fish, like in Aqua Real. My 4 year old daughter, using Aqua Real, feeds her fish everyday and night. At one point I thought that she really thought they were real, so after her and her brothers got back from a sleep over at their grandparents house I said, "While you were gone I feed your fish for you, they were really hungry"
She replied,
"Dad they are only pretend"

I felt dumb!