ProShares Ultra Bloomberg Natural Gas (NYSEARCA:BOIL – Get Free Report) were down 7% on Tuesday . The stock traded as low as $17.28 and last traded at $17.38. Approximately 6,789,973 shares changed hands during mid-day trading, a decline of 35% from the average daily volume of 10,525,932 shares. The stock had previously closed at $18.68. […]