Rotifers are an essential starting live food for many fish and crustacean larvae in marine hatcheries. Recently, high-density intensive systems for the culture of the rotifer Brachionus plicatilis were initiated as an alternative for the traditional batch culture systems. Among the most common problems facing intensive culture systems,is the accumulation of dissociated ammonia (NH3) which hinders the development of this technique. This study was conducted to test the effect of different ammonia removal compounds on the population growth of the rotifer, Brachionus plicatilis in an intensive system. The experimental closed-system design is composed of a rearing tank (100l capacity), a protein skimmer and a settling tank. Rotifers were fed with concentrated microalgae cells, Nannochloropsis oculata(3 x 109 cell/ml) and each experiment lasted for 10 days at 24C0. To investigate the effect of ammonia removers
on population growth of rotifers, two commercial water conditioners were used (ChlorAm-X®, sodium hydroxymethanesulfonate, Aqua Science Research Group, Inc., MO, USA., added daily at a rate of 0.25 gm/106 rotifers) and (Ammo-Lock*, a registered trademark of Mars Fishcare, North America, Inc. added once at one gm/1l
of culture water). At the end of each experiment, rotifer population numbers ranged from 300 – 1800 individual/ml. The best treatment method to get rid of ammonia and attain high population growth rates of rotifers was the use Ammo-Lock* followed by ChlorAm-X®.