Hi,
In your RotBucket class, add this :
public ItemStack onFoodEaten(ItemStack par1ItemStack, World par2World, EntityPlayer par3EntityPlayer)
{
par3EntityPlayer.addPotionEffect((new PotionEffect(Potion.nightVision.getId(), 100, 0)));
par3EntityPlayer.addPotionEffect((new PotionEffect(Potion.wither.getId(), 100, 0)));
}