This is Newt's current set up with the two sputniks, and a second corner shelf - his house is underneath the shelf in this set up. The large cork log at the front in the middle is good - its a ramp up to both the door and the second sputnik and he can get to the shelf from the sputnik through the tube. It also makes a nice big dark tunnel from one end of the cage to the other.
Also not just overhead cover maybe - but they do need somewhere dark to retreat to and I've found putting a bendy bridge tunnel over the house door keeps them happy too as it makes the house dark inside.
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Attachment 47026