science has just discovered a better and cheaper medium for growing fish food. Researchers from West Bengal's Kalyani University recently found human urine could be an excellent liquid incentive for mass production of the minute flea Moina micrura, a widely used fish food.

"The crustacean, also called water flea, is highly preferred feed for commercial fish,' says B B Jana, lead author of the paper. The team carried out a mass culture of M micrura in 24 outdoor tanks to study the nutrient potential of human urine and compare its efficacy with other waste materials such as cow urine.

The team found that the organism cultured in human urine started reproduction 4 days earlier than those cultured in other wastes. The paper has been published in the journal Ecological Engineering (August 1, 2007).

"Human urine degrades rapidly in the presence of oxygen and releases nitrogenous materials like proteins and minerals. This aids growth and reproduction of M micrura. A large number of bacteria also develop during the process, improving the water flea's growth. This property of human urine makes it distinct from other waste materials like cow urine,' says Jana. "One can get the best result within seven days of human urine culture,' he adds.

But the concentration of urine has to be kept in a safe range. Though the scientists are still working on the optimum urine concentrate, they say that the best results come at the concentration of 0.11 ml per litre. The scientists say that the organism can die within an hour if the concentration rises beyond 15 ml per litre. They are working out the cost of the process.