That's only 50ml though. I don't think anybody actually tried to put a large amount of water in zero g, but I would guess that unless it's a really large amount and it can hold by its own gravity, it wouldn't form a bubble. Maybe if you gradually add water through the center with a straw? I don't know... However I think it would totally stick together, so a fish would be mostly fine if there's enough water. But then would it care about not knowing where up is and not be able to move or would it start doing flips and barrel rolls? Would it know where the edge is or just fly out to its death?
Once again, Giantbomb.com, your home for all the important scientific quandries.
I just Google'd "fish in space" and apparently there has been experiments with fish in zero-G environments. They even have an aquarium on the ISS. There are already videos of people messing with water in space so the water would hold too.
Edit: and I don't think the fish will swim out of the water either, unless they're the dumb type that throws itself onto the ground and dies on Earth.
Fish in a space station: Totally plausible. There may be less gravity, but hydrogen bonding and pressure would allow the water molecules to stay together to provide a medium for movement. Also oxygen in the ship would allow for diffusion through the water bubble for the fish to breath.
Fish in open space: Absolutely not plausible. The vacuum of space and the extremely cold temperatures would cause liquid water to immediately become vapor. This isn't dissimilar to the "water gun on a cold day" analogy you can find on YouTube. The fish would turn into a block of frozen molecules, like every space death you've ever seen.