Edgar,
This is a very slight glitch and probably doesn't affect many people. I have been sitting watching sharks in 3d using my shutter glasses, and have found a slight problem for viewing in stereo 3d. I'm not sure if this is how you would explain it, but here it goes.
Set up:
The best analogy I can come up with is that the front limit of the tank is slightly off. I am assuming that programing sets a front limit and a back limit for the depth to be used. I have seen 3d images work in several different ways. The test stereo image that comes with the nvidia stereo drivers looks like it is coming out of the front of the screen and floating in air. Since I have IR glasses as well as wired glasses I can stand all the way across the room and look if I wish. The farther away I stand, the farther it looks like the image is coming out of the screen. Jim's aquarium on the other hand looks like it goes deeper into the screen and doesn't have fish floating in the air at all, so I assume he set a limit to keep this from happening.
Problem:
In watching sharks, when one swims directly towards the front of the screen and grows larger and larger at the very end when it is at its largest it looks like it is sticking ever so slightly out of the front of the screen for a few seconds and then it "snaps" back and turns in a different direction and either reverses course or swims to one side or the other and leaves the screen momentarily. That "snap" is very noticable, like someone jerked it back by its tail. So I am guessing that the front limit is slightly off from what should be allowed. I'm not sure how important this is in the "grand scheme" of things, if you are considering stereo 3d as part of the product options or just a "bonus" so to speak. But if you are considering it, it needs looking into.
Addition:
As far as stereo 3d goes, if you are considering it in your product line, I would like a check box to allow sharks to swim out from the screen a short amount. Not enough to make it look totally unreal or stupid, but just enough to get a true outwards 3d effect. To keep problems like this from happening, I would suggest that any fish past the "front line" of the screen if the box is checked be forced to reverse course and swim back behind the "front line" before turning off the screen. It might be a draw that brings attention to your screen saver over others, because I can't think of any that market "true stereo 3d" along with their product.
Just a thought.
FYI:
For whats its worth, sharks looks pretty good in 3D.