diff --git a/source/net/yacy/kelondro/blob/ArrayStack.java b/source/net/yacy/kelondro/blob/ArrayStack.java
index 72d83e51f..f93421f0e 100644
--- a/source/net/yacy/kelondro/blob/ArrayStack.java
+++ b/source/net/yacy/kelondro/blob/ArrayStack.java
@@ -41,7 +41,9 @@ import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorCompletionService;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.FutureTask;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -561,7 +563,7 @@ public class ArrayStack implements BLOB {
             if (bi.blob.containsKey(key)) return bi;
             return null;
         }
-        
+
         // first check the current blob only because that has most probably the key if any has that key
         int bs1 = this.blobs.size() - 1;
         blobItem bi = this.blobs.get(bs1);
@@ -572,7 +574,7 @@ public class ArrayStack implements BLOB {
             if (bi.blob.containsKey(key)) return bi;
             return null;
         }
-            
+
         // start a concurrent query to database tables
         final CompletionService<blobItem> cs = new ExecutorCompletionService<blobItem>(this.executor);
         int accepted = 0;
@@ -839,30 +841,35 @@ public class ArrayStack implements BLOB {
             final blobItem bi = this.blobs.get(0);
             bi.blob.delete(key);
         } else {
-            final Thread[] t = new Thread[this.blobs.size() - 1];
+            @SuppressWarnings("unchecked")
+            final FutureTask<Boolean>[] t = new FutureTask[this.blobs.size() - 1];
             int i = 0;
             for (final blobItem bi: this.blobs) {
                 if (i < t.length) {
                     // run this in a concurrent thread
                     final blobItem bi0 = bi;
-                    t[i] = new Thread() {
+                    t[i] = new FutureTask<Boolean>(new Callable<Boolean>() {
                         @Override
-                        public void run() {
+                        public Boolean call() {
                             try { bi0.blob.delete(key); } catch (final IOException e) {}
+                            return true;
                         }
-                    };
-                    t[i].start();
+                    });
+                    DELETE_EXECUTOR.execute(t[i]);
                 } else {
                     // no additional thread, run in this thread
                     try { bi.blob.delete(key); } catch (final IOException e) {}
                 }
                 i++;
             }
-            for (final Thread s: t) try {s.join();} catch (final InterruptedException e) {}
+            // wait for termination
+            for (final FutureTask<Boolean> s: t) try {s.get();} catch (final InterruptedException e) {} catch (ExecutionException e) {}
         }
         assert mem() <= m : "m = " + m + ", mem() = " + mem();
     }
 
+    private static final ExecutorService DELETE_EXECUTOR = Executors.newFixedThreadPool(128);
+
     /**
      * close the BLOB
      */