Many species belong to the class Rotatoria, but the one most suitable for mass culture appears to be Brachionus plicatilis. It is a very important and indispensable food for marine fish larvae and has also been used on a large scale during the last decade as food for the mysis stages of penaeid prawns (Liao et al., 1999).

The size of B. plicatilis ranges between 100 and 400 µm. B. plicatilis can be separated into three strains: the L-type (190 to 320 µm), the S-type (140 to 220 µm), and the SS-type (100 to 160 µm).

B. plicatilis is eurythermal. When the water temperature declines below 10^°C, dormant eggs are formed. It still grows at 15^°C, but does not reproduce. Between 15 and 35^°C, the growth rate of B. plicatilis increases with temperature. However, its life-span is shorter at high water temperatures. The optimum water temperature for its growth is 22 to 30^°C varying according to size types. The optimum range of salinity for this species is 10 to 35 ppt (Liao et al., 1993).

Intensive production of rotifers is usually performed in batch culture in indoor facilities, based on the asexual reproduction of the animals. Two methods exist for the mass culture of B. plicatilis, according to the size of the tank and the process of harvesting. One is the changing-tank method and the other is the partial-harvest method (Liao et al., 1993).

Food used as feed for B. plicatilis is varied and includes microalgae, bacteria, yeast, and microorganic particles. The best foods are a combination of microalgae (e.g., Chlorella and Tetraselmis) and bread yeast. B. plicatilis, fed solely on bread yeast, is as good a diet for P. japonicus as rotifers fed Nannochloropsis, as demonstrated in feeding experiments (Liao et al., 1993).

Contamination by copepods or ciliates in the rotifer culture tank is a serious problem. Both compete for food with rotifers and inhibit, in many cases, the growth of the latter. In addition, some copepod species are predators of rotifers. Accordingly, attention must be paid to prevent contamination by copepods and ciliates (Liao et al., 1993).

Small-scale harvesting of rotifers is usually performed by siphoning the content of the culture tank into filter bags with a mesh size of 50-70 µm. If this is not performed in submerged filters damage to the rotifers can be important and result in mortality. Therefore, it is recommended to harvest under water. Very convenient for this purpose are the concentrator rinsers (Dhert, 1996). After harvest rotifers are then released into larval tanks. If the salinity of the larval tank is the same or slightly different from that of the rotifer culture tank, most of the rotifers in the larval tank may survive for 1 d. If the salinity of the larval tank is under or above 15 ppt of that of the rotifer culture tank, only 50% of the rotifers may survive for 1 d. The density of rotifers applied to the larval tank may range between 5 and 30 individuals per milliliter (Liao et al., 1993).