In the latest Java snapshot, the tropical fish can now spawn inside lush caves on waters in the clay pool, which can be useful to breed axolotl in their natural habitat. However, on Bedrock, they don't spawn on lush caves yet.
Step to Reproduce
1. Find a lush cave.
2. Try to find any tropical fish.
Tropical fish can spawn inside lush caves.
No tropical fish spawning inside lush caves.
You can check the addon behavior pack template to see if tropical fish can spawn inside lush caves.