Culture of fish food organisms

Unit 2 - Rotifers

2.3.2.General culture conditions
Intensive production of rotifers is usually performed in batch culture within indoor facilities; the latter being more reliable than outdoor extensive production in countries where climatological constraints do not allow the outdoor production of microalgae. Basically, the production strategy is the same for indoor or outdoor facilities, but higher starting and harvesting densities enable the use of smaller production tanks (generally 1 to 2 m³) within intensive indoor facilities.

Salinity:
Although Brachionus plicatilis can withstand a wide salinity range from 1 to 97 ppt, optimal reproduction can only take place at salinities below 35 ppt.

Temperature:
Rearing rotifers at high temperature enhances the cost for food. This is essential for the maintenance of good water quality, and to avoid periods of overfeeding or starvation which are not tolerated at suboptimal temperature levels. For example, at high temperatures starving animals consume their lipid and carbohydrate reserves very fast. Rearing rotifers below their optimal temperature slows down the population growth considerably.

Dissolved oxygen:
Rotifers can survive in water containing as low as 2 mg.l-1 of dissolved oxygen. The level of dissolved oxygen in the culture water depends on temperature, salinity, rotifer density, and the type of the food.

pH:
Rotifers live at pH-levels above 6.6, although in their natural environment under culture conditions the best results are obtained at a pH above 7.5.

Ammonia (NH3):
The NH₃/NH₄₊ ratio is influenced by the temperature and the pH of the water. High levels of un-ionized ammonia are toxic for rotifers but rearing conditions with NH₃ concentrations below 1 mg.l-1 appear to be safe