• A common old wives tale is that fish grow to the size of the aquarium. Actually they will continue to grow as long as they have a quality environment. To find out, a group of researchers kept several trout in 3-inch diameter tubes. Clean water was constantly circulated through the tubes. The trout eventually grew to fill the tubes completely!
• King Angelfish Holocanthus passer act as cleaner fish for Hammerhead sharks. They can be seen picking parasites from inside the sharks' mouth! (As it turns out many of the Holocanthus angelfish act as cleaner fish).
• The Livingtonii Cichlid Crytocara livingstonii from Lake Malawi in Africa has an unusual behavior! It will "play dead" on the bottom of the aquarium, lying on its side for long periods of time. When smaller fish approach as if to nibble at the dead carcass, they are captured with a lightning quick lunge! From this behavior originated the German name for these fish, the "Sleeper".
• An interesting characteristic of the Three-spot, Blue, Gold, Opaline and Pearl Gourami, is that they are well known for eating hydra. The hydra is a tiny pest that has tentacles with a venom. Very small fish that come in contact with the hydra are paralyzed by the venom and then held fast by the tentacles until eaten by the hydra.
