We were convinced it made our fish happier

When I was in college, my roommate and I had five aquariums of various shapes and sizes in our apartment. Two aquariums sat side by side on a shelf, and we connected them by inserting one end of a U-shaped piece of PVC pipe into each aquarium. (Somehow we got water into the pipe, and the laws of physics kept it there.) This allowed the fish to swim from one aquarium to the other. They used this "Fish Habitrail" quite a bit, and we were pretty impressed with ourselves.

Now that I've seen this, I don't think we dreamed big enough.

(Ours looked very much like the one shown in this patent from 1877)