Just like in real life, it is quite good to get some fish. They contain a lot of protein and are a great source of healthy fats, so I would not avoid them entirely. However, fishes should not be used as a substitute for love. You need a bit of both. It's probably best to get mostly love, though. You can't eat that much fish when you're full. A good ratio is one fish per four loves (both in the game and in real life).
Thank you for playing!