This is a very simple mod that stops bats and fish (cod, salmon, pufferfish, tropical fish) mobs from spawning.
It does that by stopping the spawns of any Ambient and Water ambient mobs.
These mobs are labeled ambient because they are primarily used for well ambience!
They don't have much or any use. It will also disable any modded mobs that are labeled ambient too.
I made it after I found out 5% of the server's CPU was taken by ambient mobs.
As I thought the trade off was not worth it in the least, I decided to just remove them.
I even played minecraft before they were even added, so it doesn't really matter.
If someone wants, I think it'd be possible to make ambient mobs truly ambient, by making them client side only.
That way you could still see fish swimming around, and even kill them, but the server wouldn't need to do anything.
This is a mod meant for servers who want to squeeze every bit of performance they can. You probably won't feel much of a difference on singleplayer.
Note: it doesn't despawn currently existing mobs.
