Steps to Reproduce:
1. enable deferred rendering shaders
2. find any fish/tropical fish
3. view z fighting on all fins

Observed Results:
all fins on all fish have z fighting with deferred shaders on.

Expected Results:
The tropical fish default material needs to have the "DisableCulling" state removed.

I have managed to fix the issue like this:
"tropicalfish:entity_multitexture_multiplicative_blend": {"-states": ["DisableCulling"]}