Juvenile fish in exponential growth phase are placed, after being weighed, in test chambers and are normally exposed to five sublethal concentrations of the test substance dissolved in water preferably under flowthrough, or, if not possible, under appropriate semi static (static-renewal) conditions. The test duration is 28 days. The daily food ration is based on initial fish weights and may be recalculated after 14 days. The study report should include the concentration measurement of the test substance, the observation of external abnormalities and abnormal behavior and the fish weighting at the end of the test. Effects on growth rates are analyzed using a regression model in order to estimate the concentration that would cause a x % variation in growth rate, i.e. ECx. Alternatively, the data may be compared with control values in order to determine the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC).