NEW YORK (TheStreet) -- Here are my ETF winners and losers for this week.
Guggenheim Solar ETF ( TAN) -2.6% The solar energy ETF struggled to gain footing over the past week, even as investors learned that Warren Buffett's Berkshire Hathaway ( BRK.A) had taken a
dramatic step into the industry. On Friday, I explained that many of the same factors that have threatened TAN and other alternative energy ETFs in 2011 continue to be in play. It may be tempting to follow Buffett's lead here, but I urge investors to hold off. This is not a sector for the faint for heart. United States Natural Gas Fund ( UNG) -7.2% UNG and other futures-linked natural gas ETFs tumbled to all-time lows this week as issues like oversupply weighed heavily on the fuel's prospects. I've encouraged investors on a number of occasions to steer clear of these funds. An equity-backed option like the First Trust ISE Revere Natural Gas Index Fund ( FCG) (FCG) is a far safer choice for natural gas bulls. Written by Don Dion in Williamstown, Mass.