diff --git a/tapqir/models/cosmos.py b/tapqir/models/cosmos.py
index 1e5717c..8917fea 100644
--- a/tapqir/models/cosmos.py
+++ b/tapqir/models/cosmos.py
@@ -190,8 +190,6 @@ def model(self):
             dim=-1,
         )
 
-        # spots
-        spots = pyro.plate("spots", self.K)
         # aoi sites
         aois = pyro.plate(
             "aois",
@@ -258,7 +256,7 @@ def model(self):
                     onehot_theta = one_hot(theta, num_classes=1 + self.K)
 
                     ms, heights, widths, xs, ys = [], [], [], [], []
-                    for kdx in spots:
+                    for kdx in range(self.K):
                         specific = onehot_theta[..., 1 + kdx]
                         # spot presence
                         m = pyro.sample(
@@ -369,8 +367,6 @@ def guide(self):
             ),
         )
 
-        # spots
-        spots = pyro.plate("spots", self.K)
         # aoi sites
         aois = pyro.plate(
             "aois",
@@ -418,7 +414,7 @@ def guide(self):
                         ),
                     )
 
-                    for kdx in spots:
+                    for kdx in range(self.K):
                         # sample spot presence m
                         m = pyro.sample(
                             f"m_k{kdx}",
diff --git a/tapqir/utils/dataset.py b/tapqir/utils/dataset.py
index 70dbb78..931fbfd 100644
--- a/tapqir/utils/dataset.py
+++ b/tapqir/utils/dataset.py
@@ -138,10 +138,16 @@ def median(self) -> torch.Tensor:
         )
 
     def fetch(self, ndx, fdx, cdx):
+        if isinstance(ndx, torch.Tensor):
+            ndx = ndx.cpu()
+        if isinstance(fdx, torch.Tensor):
+            fdx = fdx.cpu()
+        if isinstance(cdx, torch.Tensor):
+            cdx = cdx.cpu()
         return (
-            Vindex(self.images.to(self.device))[ndx, fdx, cdx],
-            Vindex(self.xy.to(self.device))[ndx, fdx, cdx],
-            Vindex(self.is_ontarget.to(self.device))[ndx],
+            Vindex(self.images)[ndx, fdx, cdx].to(self.device),
+            Vindex(self.xy)[ndx, fdx, cdx].to(self.device),
+            Vindex(self.is_ontarget)[ndx].to(self.device),
         )
 
     @lazy_property