While I play Minecraft, my spawn is usually far away from a coral biome, and sometimes I like to bring fish back in buckets. Is there something that you can do, maybe place certain blocks (Like to breed pandas) to make your fish breed with each other? Is there a way to breed fish, so I don’t have to go back to the coral biome every time one of my fishes dies?
No.
You cannot breed Fish. There are no Baby Fish in Minecraft. Fish spawn naturally in Ocean Biomes, like passive mobs do on land.
– How do you breed fish? – Reddit
The Wiki article also never mentions anything about breeding.
Fish can only spawn underwater at a Y level of 12-32.
Cod spawn in normal, cold, and lukewarm oceans, and their deep variants in groups of 4-7.
Pufferfish spawn in lukewarm, warm, and deep lukewarm oceans in groups of 3-5.
Tropical fish can only spawn in warm ocean in groups of 3-5.
Salmon spawn in groups of 3-5 in cold and frozen oceans, and their deep variants. Unlike the other types of fish, they also spawn in normal and frozen rivers. Salmon can spawn in 3 sizes which are small, normal and large.
– Fish (mob) – Minecraft Wiki
So the ways listed above are the only ways fish can spawn.