Fun and cute little music programming game! 🎵 Love that it was made with Tic-80. The graphics are really nice. I do wish the order of appearance of the fish already informed in what order they were going to sing, as usually I would feed them so that they would sing in that order anyway. I also wish it was easier to tell the different types of fish apart when they're in the pond.
If you keep working on this and want to lean into the puzzle aspect I would suggest an action counter (or maybe even a limited action count?) so that there would be a challenge in completing all the objectives with as few player actions as possible, re-using the same fishes etc.
As it is it's already a nice creative toy that's fun to explore! :)