I really LOVE the art style. The crab's eyes following my mouse cursor put a big smile on my face.
I had a lot of fun playing and was impressed with all the fish variations. I took me a minute to realize my fish could attack back, but once I did, it opened up the game for me. I was confused at Arcade mode at first, but I think you have a fun concept with the breeding pairs.
I'd love an option to reset the level after I made a mistake or lost my goal fish. I also felt like each stage in Puzzle mode should end after the goal fish made it to safety.
Really great work! I'd love to see you continue to develop this game.