I like that idea! You could take the best, most feasible suggestions from users of both Plant and Fish Tycoon and use them to create a pretty cool complex simulation. Like Flash57 said, you could get very creative with what the game player could do with the output of breeding efforts: dead fish fertilizer, selling seed packets, even a little chemistry lab on the side for developing new concoctions to pour on your plants or dump in your fish tank! You already have a lot of the code to serve as a launch pad for it, too.