The Reef Stonefish is the most venomous fish in the world. It has thirteen stout spines in the dorsal fin which can inject a highly toxic venom. The venom causes intense pain and is believed to have killed many Pacific and Indian Ocean islanders. No deaths have been recorded in Australia since European arrival (Underhill, 1987). An antivenom developed in 1959 further reduces the likelihood of death. Despite this, many people suffer the agony of a sting every year. Very hot water (not scalding) can be used to relieve the pain, but medical treatment should be sought.
Reef Stonefish grow to 35 cm in length, although 50 cm 'monsters' have been reported. They are extremely well camouflaged, looking like an encrusted rock or lump of coral. Reef Stonefish are usually brown or grey and may have patches of yellow, orange or red. They usually live on rubble or coral bottoms, often under rocks or ledges, but are also known to be able to bury in sand using their large pectoral fins.
The Reef Stonefish is widely distributed throughout tropical, marine waters of the Indo-Pacific. In Australia it is recorded from much of the Great Barrier Reef, Queensland, to far northern New South Wales.
The Reef Stonefish eats fishes and crustacea. It usually waits for prey to swim past, and then strikes with incredible speed. High speed camera equipment is required to record the feeding of this species.
Predators of the Reef Stonefish include sharks and rays. Jeff Johnson, Fish Collection Manager at the Queensland Museum stated, "I have seen stonefishes in gut contents of large sharks (tigers and white pointers). Also small stonefishes are taken by Stokes Sea Snake, Astrotia stokesii. Stonefish bones have also been found in Aboriginal middens.".
View low resolution movie clips of the head of a stonefish (91k)and a stonefish swimming (58k). Go to the movies page for high and low resolution versions.
Two species of stonefishes are recorded from Australia, the Reef Stonefish and the Estuary Stonefish, Synanceia horrida . One of the ways to tell the two species apart is the placement of the eyes. The eyes of the Reef Stonefish are separated by a deep depression, however those of the Estuary Stonefish are elevated and separated by a bony ridge.
http://www.amonline.net.au/fishes/students/focus/sverruc.htm
i found this through a google hope it helps
why keep a lethal fish in a small tank? 
