Minecraft wiki entry for Tropical_Fish, associated text: Entity data
Tags common to all entities[show]
Tags common to all mobs[show]
 FromBucket: 1 or 0 (true/false) - Whether the fish had ever been released from a bucket.
 Variant: A 4-byte integer.
The least significant byte has a value of either 0 for a small fish, or 1 for a large fish. Values above 1 result in an invisible fish.
The next byte has a value from 0–5, representing the pattern on the fish. Values above 5 result in a fish with no pattern.
The next byte has a value from 0–15, representing the color of the fish's body.
The most significant byte has a value from 0–15, representing the color of the fish's pattern.