Hi,

The simplest approach is to culture them using media with a salt level matched to seawater. I think Marine Agar is made like that.

A simple method would be use agar (nutrient agar) medium with different concentration of NaCl (1 to 1.9%; sea water has 19g/L of NaCl) and streak your probiotic culture on the plates. This will give you some idea on salt tolerance level of the probiotic. Plus check the salt concentration of the water that you are using for the fish culture.

Also in what way you are feeding the probiotic matters, example, you can feed through fish feed and you may use some protectants (encapsulation of the probiotic cells) so that the probiotic won't be exposed to salt and the capsule will release the probiotic during digestion.

Thanks for the advice :D

I would try it :D