Haven't they got fish on the ISS or taken them up in the Shuttle for experiments in the past?
The first fish to go into space were two Mummichog Minnows sent in an aquatic bag on the Skylab 3 mission in 1973.
http://history.nasa.gov/SP-401/ch17.htm
http://www.nasaimages.org/luna/serv...87~138754:Personnel-observe-minnows-to-be-sen
The top ten animals in space:
http://www.toptenz.net/top-10-animals-astronauts-in-space.php