Complex sentence: The Belle Isle Aquarium reopened on August 18,2012 and is now run entirely by volunteers prior to that it opened on August 18,1904, and was the oldest continually operating public aquarium in North America when it closed on April 3,2005.
Split into simpler sentences: The Belle Isle Aquarium reopened on August 18,2012 and is now run entirely by volunteers. It had originally opened on August 18,1904 and was the oldest continually operating public aquarium in North America when it closed on April 3,2005.