Fishies!

[kario]

I think that you should be able to "breed" fish like a chicken coop.
they should be built on a pond (another idea) or a big bucket (another one) sort of thing.
The fish should be gotten from fishing the river.
Fish should also only be able to "breed" with their own kind or just another container all its own for each kind.

[Serpensio]

I'd rather have a Rabbit Hutch first, but a fish pond is a good idea too.

[SacreDoom]

try using the search function another time.