Minecraft wiki entry for Tropical_Fish, associated text: In Bedrock Edition, tropical fish spawn underwater at 12-32 blocks away from the player. Tropical fish spawn only in warm, lukewarm, deep lukewarm ocean biomes and lush caves, in groups of 3-5 for the same preset pattern, and in groups of 1-3 for a random pattern. In addition, tropical fish in warm, lukewarm ocean and deep variants can only spawn at Y levels between 50 and 64 and must be on the surface (i.e., there must not be a spawnable block above the spawn location with a non-solid block on top). Tropical fish in lush caves can spawn on any Y levels but require underground.