The Deep Freeze

Can someone give me a physics lesson?  Each
time I blip the unfrozen part of the pond where
the bubbler is the pattern is different.  It
has become a fascination for me.  It must
have to do with temperature drop. i.e. how
fast the temperature drops.  Note how the
bubbles froze in their own round shapes in
the unfrozen circle. 

On a slightly different note, this morning the
pond is totally frozen over, but there is still
oxygenated water because the bubbler is
at work under the ice.  Are my goldfish still
alive and breathing?   It is -4 degrees f. and many
schools are closed.  Darn this cold snap best
''snap out of it.''