Lying in wait for the Bobbitt worm

Miranda Green at the FT on the charms of marine life in the living-room:

t’s half past one in the morning and Jessica Cross, a top metals analyst in the City, is wired. But she’s not poring over the latest figures or sweating to get a report finalised.

Instead she is lying in wait for a Bobbitt worm, the nocturnal predator that has invaded the tropical marine ecosystem she spent the past two years creating in her central London apartment. The creature in her fish tank is only three feet long, but could grow up to 12ft, and Cross is worried that, although there are only a few crabs missing, the worm might start eating the rare fish.

“Sometimes in the middle of the night I do think, what have I done?” admits Cross, confessing she has become obsessed with the tank and its inhabitants. She gazes admiringly at the pulsing green and pink anemones. It is daylight when she shows me the collection: exotic clams shiver along frills like painted silk while striped and spotted fish swim by a red mantis shrimp, with the appearance of a tiny Chinese dragon, peering out from under the coral.

A lifelong interest in marine biology led Cross, originally from South Africa, to set up the tank, which now absorbs a sizeable chunk of her time and energy, day and night. She is one of what Nick Lloyd at the Aquatic Design Centre in Great Portland Street estimates to be several hundred individuals in the capital who have tried to painstakingly recreate “a little piece of the ocean in their living room”.

For these are no ordinary fish tanks. The water is mineralised to mimic the sea, and sand is added along with live rock containing the micro-organisms needed to generate an ecosystem. Temperature and lighting controls imitate conditions in the tropics and allow true enthusiasts to introduce not only colourful fish but corals, which are extremely difficult to look after.

The rising number of reef tank enthusiasts has been fuelled by improved technology and a growing awareness of environmental damage to the world’s coral reefs. Only in the past 10 years or so has it been possible for the home hobbyist to even try because coral will die unless the temperature is kept within a very narrow band – 26°-28°C – and the smaller the volume of water, the more difficult it is to keep the environment stable.