how do I fix this script so the instantiations destroy or get pooled correctly.?

how do I fix this script so the instantiations destroy or get pooled correctly. the spawns wander off screen and stay in space forever slowing game down and how di I change script so the instantiations keep instantiating not just once as it is now, the way it is now the objects pooled get instantiated once and that's it, I want them to keep instantiating every few seconds but dont wander in space they get destroyed or stopped then pooled form beginning again

I see the instantiations going off screen and adding up staying in the scene, I thought the point of pooling is to reuse the same instantiations

I see the inspector keep creating clones of the enemy, so please help how do I poo l these enemies and destroy them so they dont wander off screen in space forever as they now are

2d game

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class ObjectPool : MonoBehaviour
 {
     public static ObjectPool current;            //A public static reference to itself (make's it visible to other objects without a reference)
     public GameObject[] prefabs;                //Collection of prefabs to be poooled
     public List<GameObject>[] pooledObjects;    //The actual collection of pooled objects
     public int[] amountToBuffer;                //The amount to pool of each object. This is optional
     public int defaultBufferAmount = 10;        //Default pooled amount if no amount abaove is supplied
     public bool canGrow = true;                    //Whether or not the pool can grow. Should be off for final builds
 
     GameObject containerObject;                    //A parent object for pooled objects to be nested under. Keeps the hierarchy clean
 
 
     void Awake ()
     {
         //Ensure that there is only one object pool
         if (current == null)
             current = this;
         else
             Destroy(gameObject);
         //Create new container
         containerObject = new GameObject("ObjectPool");
         //Create new list for objects
         pooledObjects = new List<GameObject>[prefabs.Length];
 
         int index = 0;
         //For each prefab to be pooled...
         foreach ( GameObject objectPrefab in prefabs )
         {
             //...create a new array for the objects then...
             pooledObjects[index] = new List<GameObject>(); 
             //...determine the amount to be created then...
             int bufferAmount;
             if(index < amountToBuffer.Length) 
                 bufferAmount = amountToBuffer[index];
             else
                 bufferAmount = defaultBufferAmount;
             //...loop the correct number of times and in each iteration...
             for ( int i = 0; i < bufferAmount; i++)
             {
                 //...create the object...
                 GameObject obj = (GameObject)Instantiate(objectPrefab);
                 //...give it a name...
                 obj.name = objectPrefab.name;
                 //...and add it to the pool.
                 PoolObject(obj);
             }
             //Go to the next prefab in the collection
             index++;
         }
     }
 
     public GameObject GetObject( GameObject objectType)
     {
         //Loop through the collection of prefabs...
         for(int i=0; i<prefabs.Length; i++)
         {
             //...to find the one of the correct type
             GameObject prefab = prefabs[i];
             if(prefab.name == objectType.name)
             {
                 //If there are any left in the pool...
                 if(pooledObjects[i].Count > 0)
                 {
                     //...get it...
                     GameObject pooledObject = pooledObjects[i][0];
                     //...remove it from the pool...
                     pooledObjects[i].RemoveAt(0);
                     //...remove its parent...
                     pooledObject.transform.parent = null;
                     //...and return it
                     return pooledObject;
                     
                 }
                 //Otherwise, if the pool is allowed to grow...
                 else if(canGrow) 
                 {
                     //...write it to the log (so we know to adjust our values...
                     Debug.Log("pool grew when requesting: " + objectType + ". consider expanding default size.");
                     //...create a new one...
                     GameObject obj = Instantiate(prefabs[i]) as GameObject;
                     //...give it a name...
                     obj.name = prefabs[i].name;
                     //...and return it.
                     return obj;
                 }
                 //If we found the correct collection but it is empty and can't grow, break out of the loop
                 break;
                 
             }
         }
 
         return null;
     }
 
     public void PoolObject ( GameObject obj )
     {
         //Find the correct pool for the object to go in to
         for ( int i=0; i<prefabs.Length; i++)
         {
             if(prefabs[i].name == obj.name)
             {
                 //Deactivate it...
                 obj.SetActive(true);
                 //..parent it to the container...
                 obj.transform.parent = containerObject.transform;
                 //...and add it back to the pool
                 pooledObjects[i].Add(obj);
                 return;
             }
         }
     }
     
 }