.

Antibiotics have been widely used in aquaculture in sterilization of equipments and in treatment of fish diseases, and
control of bacteria infections in fish hatcheries. However, the negative effects associated with the use of antibiotics
such as development of resistant bacteria which constitute potential hazard to the environment and the people has led
credence to the use of probiotics. Probiotics are live harmless bacteria that help the well being of the host animal and
contribute directly or indirectly to protect the host animal against harmful bacteria pathogens. This paper reviews the
types of natural and synthetic/commercial probiotics available for aquaculture; the selection criteria for probiotics;
some techniques or parameters used in the assessment of the performance of probiotics and specific effects of some
probiotics on aquaculture. The findings showed that probiotics are useful in reducing anti-nutritional factors (tannin,
phytic acid, mimosine) in non-conventional fish feed ingredients; in improving water quality and the growth of fishes
and in immune stimulation in fishes; in increasing the population of native non-pathogenic bacteria and digestive
enzyme activities; and in inhibition of pathogenic organisms and reduction in incidence of diseases. Probiotics are
also environmentally friendly therefore their use in aquaculture is indispensable.