I don't know how he recirculates the sand...
https://www.youtube.com/watch?v=1aETKRPkmJs
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I don't know how he recirculates the sand...
https://www.youtube.com/watch?v=1aETKRPkmJs
Quite a fun video on the same topic.
https://www.youtube.com/watch?v=kFUTDIsQrlQ