This is a texture pack that adds/adjusts the tropical fish bucket textures to reflect the fish inside. The creative tool bucket is unchanged. It does not require any mods.
The 22 more common named fish variants are denoted as such by a slight blue bucket tint.
A version without the bucket tint is available.
This only works for 1.21.5+ Versions for 1.21.4 or behind are unlikely, due to mod necessity.