Yea, I looked through the comments and many people raised the question, though the person with the tank only responded to a couple and seemed to completely miss the point of the question. Many people don't understand why the water would stay in it at all, so that distracts from the people who get that, but don't see how it doesn't fail due to the air stone.

The habi-trail in the restaurant is pretty cool, but I don't think it would be worth the time and expense. Doing it with actual hamster tubes would be silly I think. I agree though that it would be easy to do it and have it be corny. Plus, you would need to have two tanks with water qualities and fish species you would want to mix. Typically we select our fish populations according to our goals for the tank, this would get them all mixed up! :-)

That said, I could see some sort of sculpture type arrangement where maybe several aquariums cascade from one to the next and the fish could go with the water to the next aquarium. Of course there would need to be a way for the water, and presumably the fish to get back to the top aquarium. And if that mechanism failed, you would be in big trouble! The YouTube tank provided a unique design in a relatively simple system. It would still be a problem if it were all released into the main tank I imagine, but we're talking a failure of a silicone tank seal then. You could easily use powerheads to circulate the water air free.

Oh well.. I'm approaching half a dozen tanks totaling over 500 gallons, that's plenty! (I say that now, but... )

Michael