Shenzhen: Time to ponder

Where do all the fishies and froggies go?  They will be back.

This is our compound's pond, which just happens to be (by my calculations) on the roof of the multi-level parking building.  I admit, this isn't the first blip of this fascinating cleaning process (20 November 2014, 5 June 2014, 19 June 2013).  Every time I hear the tell-tale scrapping I can't resist.