How to best optimise this script

Hi,

I have written a script which is used to fade out enemy objects that come within a specified distance from the camera. The script is to be used for iOS devices and I was wondering if anyone can recommend how I could optimise it to make it as light as possible on performance. It uses iTween.FadeTo() to fade the object.

I know that the distance check has to be run every frame and so must be inside the Update() function, but are there other areas I can improve on? The script is attached to the MainCamera.

Any help would be great.

//---

    // Variable to hold the distance between the camera and the object
     private float Dist;
 
     // The distance at which the object will begin to fade
     public float FadeDistance;
 
     // The array of GameObjects (Enemies) in the scene that we want to be faded
     public GameObject[] Enemies;
 
     void Start()
     {
         // Find all of the object with tag "Enemy" in the scene and
         // copy them into the Enemies array
         Enemies = GameObject.FindGameObjectsWithTag("Enemy");
     }
 
     void Update()
     {
          foreach (GameObject enemy in Enemies)
          {
             // If the element is null (false) the enemy is dead, so we ignore them
             if (enemy) 
             {
                 // Find the distance between the Camera and the enemy getting its 
                 // Absolute value (positive only)
                 Dist = Mathf.Abs(transform.position.z - enemy.transform.position.z);
 
                 // if the object has tag "enemy" AND is closer than our fade distance..
                 if (enemy.collider.tag == "Enemy" && Dist <= FadeDistance)
                 {
                     // Fade the object (level of alpha (0 = transparent), time to take to fade)
                     iTween.FadeTo(enemy, 0.0f, 0.2f);
 
                     // Destroy the enemy after 1 second
                     Destroy(enemy, 1);
                 }
             }
         }
     }