diff --git a/server/bingo/admin.py b/server/bingo/admin.py
index e3d242e..0b4f10e 100644
--- a/server/bingo/admin.py
+++ b/server/bingo/admin.py
@@ -1,5 +1,6 @@
 from django.contrib import admin
 from django.contrib.auth.models import Group
+from django.forms import ModelForm, ValidationError
 
 from .models import User, Challenge, Friendship, BingoGrid, TileInteraction
 
@@ -44,8 +45,26 @@ class FriendshipAdmin(admin.ModelAdmin):
     fields = list_display
 
 
+class BingoGridAdminForm(ModelForm):
+    class Meta:
+        model = BingoGrid
+        fields = ('grid_id', 'challenges', 'is_active')
+
+    def clean_challenges(self):
+        challenges = self.cleaned_data['challenges']
+        if len(challenges) != 16:
+            raise ValidationError(
+                "BingoGrid must have exactly 16 challenges."
+            )
+        return challenges
+
+
 @admin.register(BingoGrid)
 class BingoGridAdmin(admin.ModelAdmin):
+
+    # use the above form
+    form = BingoGridAdminForm
+
     # disable the export2csv action
     def get_actions(self, request):
         actions = super().get_actions(request)
diff --git a/server/bingo/models.py b/server/bingo/models.py
index 7fa57c8..5c052a7 100644
--- a/server/bingo/models.py
+++ b/server/bingo/models.py
@@ -180,16 +180,6 @@ class BingoGrid(models.Model):
     is_active = models.BooleanField(default=False)
 
     def clean(self):
-        # Ensure exactly 16 challenges
-        # This only makes sense if the object is saved at least once (has a PK).
-        # If it's brand new, you won't have the M2M relationships set until after save.
-        if self.pk:
-            if self.challenges.count() != 16:
-                raise ValidationError(
-                    f"BingoGrid must have exactly 16 challenges (found {
-                        self.challenges.count()})."
-                )
-
         # Ensure only one active BingoGrid
         if self.is_active:
             active_count = BingoGrid.objects.filter(
diff --git a/server/bingo/tests/test_bingogrid.py b/server/bingo/tests/test_bingogrid.py
index 100ad51..6e0d72b 100644
--- a/server/bingo/tests/test_bingogrid.py
+++ b/server/bingo/tests/test_bingogrid.py
@@ -15,32 +15,6 @@ def setUp(self):
             )
             self.challenges.append(c)
 
-    def test_exactly_16_challenges(self):
-        # Verify a BingoGrid with exactly 16 challenges passes validation, but 15 or 17 fails.
-        grid = BingoGrid.objects.create(is_active=False)
-
-        grid.challenges.add(*self.challenges)
-        grid.full_clean()
-        grid.save()
-        # 15 challenge scenario
-        grid_15 = BingoGrid.objects.create(is_active=False)
-        grid_15.challenges.add(*self.challenges[:15])
-        with self.assertRaises(ValidationError):
-            grid_15.full_clean()
-
-        # 17 challenge scenario
-        extra_challenge = Challenge.objects.create(
-            name="Extra Challenge",
-            description="Extra sample challenge",
-            challenge_type="act",
-            points=10
-        )
-        grid_17 = BingoGrid.objects.create(is_active=False)
-        grid_17.challenges.add(*self.challenges)
-        grid_17.challenges.add(extra_challenge)
-        with self.assertRaises(ValidationError):
-            grid_17.full_clean()
-
     def test_preserve_challenge_order(self):
         # With SortedManyToManyField, the order we add them is retained.
         grid = BingoGrid.objects.create(is_active=False)