Potion effect on creature spawn event

Hello, Im trying to make a plugin what makes mobs harder.
This is my code now

Code:

public void onMobSpawn(CreatureSpawnEvent event){
 
if (event.getEntity() instanceof LivingEntity) {
   
event.getEntity().addPotionEffect(new PotionEffect(PotionEffectType.SPEED, 1000, 3));
 
}
}

 

You will boost animals too like that, remove them, creature spawn is for sure a LivingEntity.
Use multiplication if you want to easy calculate the lenght of the boost.

Code:java

static int duration = 20 * 60 * 5; //for 5mn example
public void onMobSpawn(CreatureSpawnEvent event) {
  if (monster instanceof Animals || monster instanceof WaterMob) return;
  else {
    event.getEntity().addPotionEffect(new PotionEffect(PotionEffectType.SPEED, duration , 3));
  }
}