Aquarium mod adds new craftable item to the game – aquarium. To fill it with water, wait for the rain. It’s useless in winter, however it may contain some ice. Fish live in it’s own life. It doesn’t work for you as slave (like bird in cage) so be careful to save it from starving.
Roe includes 0.5 meat and 0.5 fish. So roe+twig = fish sticks and so on.