The use of probiotics in feed for fish and its inclusion in intensive aquaculture to promote healthy gut is growing. The need for alternative measures that will perform closely and effectively to the use of antibiotics after its annulment in European Union (EU) in 2006 is an issue which call for concern. Several definitions of probiotics mainly for aquaculture were also dig out from published papers. Among them is a definition considered appropriate for aquaculture which is described as" any microbial cell provided via the diet or rearing water that benefits the host fish, fish farmer or fish consumer, which is achieved, in part at least, by improving the microbial balance of the fish". In this context, they regard direct benefits to the host as immuno-stimulants, improved disease resistance, reduced stress response, improved gastro intestinal morphology and benefits to the fish farmer or consumer. The benefits to the fish farmer and consumers includes improved fish appetite, growth performance, feed utilization, improvement of carcass quality, flesh quality and reduced malformations. The mode of action with benefits of probiotics in aquaculture from published journals was also looked into. The use of probiotics is growing especially as new strains were being discovered that can withstand processing stress in feed manufacturing. But process optimization knowledge to effectively work with these additives is insufficient. Combination of strain isolated from the gastro-intestinal (GI) tracts of host animal had also being proving to be effective. Need to find proper parameters to work with probiotics will be of great importance to the feed industry in the near future and the stability of the strains of probiotics as a synbiotic relation with prebiotics. Examples and effects of known strains were also stated and the future perspective of probiotics for fish.