Sharks occupy a special place in the imagination of the public but even the smallest of the species are not for the owners of domestic aquariums. They range from the pygmy shark, only 9" long to the mighty whale shark which can be 40 to 50 feet long. The pygmy shark, while suitable in size for a smaller aquarium, rules itself out by virtue of it being a deep sea creature.

Another problem with any domestic aquarium owner is that sharks have skin made from the same tissue as their teeth and it is so rough that it can be used as an abrasive! No aquarium with a touch pool would venture to have a shark on offer! Add to that, the fact that sharks are easily damaged by handling and that even the youngest, smallest ones are faster than any human and you see the problems.

Although sharks are popularly thought to swim constantly, some species dwell on the bottom of the sea, including nurse, zebras and the spotted dogfish. However, it is the streamlined grand sports cars of the sea that hold the most fascination. The 359 species of sharks do what they need to do very well, keeping effortlessly buoyant with the help of their fatty livers [which can actually float!].

Understandably, people want to see sharks and they are on view in many aquariums. There are four species on view at the London Aquarium - sand tigers, brown, nurse and zebra sharks. The aquarium had to reassure one questioner that although they fed their sharks on fish and octopus, the sharks didn't eat the fish resident in their tanks!

Visitors to the London aquarium can enjoy their sharks but to see the largest type, one needs to visit the Georgia Aquarium in Atlanta. London has a capacity of 2.5m litres [about 180,000 gallons] of water in all, but the aquarium in Atlanta has 8m gallons and 6m of that is in just one gigantic tank which the aquarium constructed in order to be able to show whale sharks. This is called Ocean Voyager by the aquarium. The acrylic viewing window is 2 feet thick! There is room for six of these fish and at present there are four of them. They are the gentle giants of the oceans, with skin that is 4 inches thick, eating plankton and small fish that drift into their four feet wide mouths. One tagged whale shark has been found to have dived one mile deep and to have travelled 2835 miles in 150 days. The aquarium is working hard to preserve the species which is under threat from unregulated fishing off China, India and the Philippines. A partnership has been formed between the aquarium and Taiwan to work together to conserve this magnificent creature.

There is one shark that belongs to the stuff of legends and is in no aquarium - the megaloden or megatooth shark. First named in 1835, and reconstructed from teeth and bits of fossilized skeleton, it lived 65m years ago and was 52 feet long and weighed 40 tons. Stories exist that it still exists, lurking in the deepest, unexplored depths. If it does, it would better if it remained there for no aquarium would welcome the financial and technical challenges of housing such a monster!