I work at an aquatic dealership in South London, and on the shop floor in the department we have a storage tank where we keep cardinals, guppies, neons, etc, ready for sale. One day I came in and noticed the tank was somewhat depleted, with no obvious dead fish floating about. On asking a colleague, he explained to me that the previous day the water in the Arowana tank had to be changed. These particular Arowanas are 20 cm long in addition to the normal Arowana traits of assault on hands with intent to munch and permanent hunger. The Arowana tank is next to the storage tank. So, when the metal grille protecting the world from the Arowanas was removed, one fish took the opportunity to attack the hand holding the net, trying to catch it. The unfortunate employee pulled his hand out quickly, giving the evil fish enough upwards momentum to clear the partition and land straight in the storage tank. Needless to say, we had lost about £40 worth of fish, and afterwards the Arowana was still hungry. Moral of the story: don't keep giant vicious tropical fish in a tank next to guppies.