I've used the real fish and the rubber ones with 7th graders.
The real ones are definetly more fun! A tip I received from someone on
this listserve a while back about the real fish is this---place them in
bleach and water( I think it was equal portions) and soak for about 15
minutes . Then rinse and soak in vinegar and water( equal portions)-dry
then freeze . It worked great. There was very little smell during the 2
hours they were used in classes..
Sid is right about the rubber ones and kids holding them by the tails. I
lost 2 of the little fins--the rubber is thin in those areas.
I've used printing ink , brushes and colored tissue. The kids go nuts
when I let them add a bit of the metallic inks to their color.