In the Breeding Lab, you can select two different species of fish as parents, and create an "unlimited" amount of uniquely looking children. You can then store your creations in your Breed Library, allowing you to add these hybrid species to your aquariums in the same way you do with ordinary species.
Please note that the current implementation is not fully polished yet and thus in a "kind of experimental" state. This basically means for you that the appearance of some cross-breeds might still be imperfect and change with future updates.
Apart for this, we have doubled the maximum allowed vertex count per aquarium, meaning you can put in more decoration items and fish. As usual, smaller bugs have been fixed as well.
Changed files in this update