http://animal-cellculture.blogspot.com/2009/06/osmolarity.html

Dear Gayatri Rajenda Kachh,

without anymore detailed info, this is a hard question. But assuming the fish is a salt water animal, it is fair to assume that its serum will be equivalent to most animals: 0.9% saline. Which is PBS. If PBS does not work,let me know.

kind regards, Harrie Verhoeven

Dear Gayatri Rajenda Kachh,

You can use fish cell culture media available from Sigma or many other manufacturer. For cell analytical purposes, you can use PBS, HBSS where cell intactness is required or water if cell lysis required.