Ok, it may not be as impressive as Gopherboy's air pump muffler but I'm well chuffed with myself. I'm quite a clumsy person and I keep breaking the glass test tubes so I've been looking for ages for a test tube holder. I was unable to find one locally and online companies seem to only sell them in bulk. So when I was unpacking my new tank, I suddenly thought "Hmmm...I wonder?"
So I cut out a rectangular piece of aeroboard/polystyrene/foam - whatever the hell that packaging is - used a circular handle to score holes of the right diameter and hey presto! One test tube holder and see, it even has a pretty pattern...Go me!