NASA and other organizations/agencies have sent fish into space, mostly tanks on the ISS or just the space shuttle.
As long as there is light coming from one direction the fish use that direction as up, when it goes dark there is no up. Nothing else really changes.
I looked at wikipedia and it looks like it's goldfish, Mummichog, zebra danio, Oyster toadfish, swordtail fish and Japanese killifish that have been sent into space.
Please ignore any spelling/grammatical errors. I'm swedish and sometimes I'm also drunk.