Thank you for your advice and the for the links Serendipity7000.
The silent runner wheel looks really cool.
I didn't want to make another topic but, does this sounds really silly? I bought some upmarket sand from Zooplus as Lucy loves her sand baths. It arrived with a leak as they haven't heat sealed the top properly. It is over the top to consider sterilising the sand? As technically with a hole in it anything could have got in it.