The explosion in ETFs enhances investment strategy options on a number of levels. One is that ETFs that hold a mix of other ETFs is now a growth industry. Indeed, as the population of strategy-specific ETFs rises, so too do the possibilties with ETF fund of funds. But as with any other ETF decision, picking a fund of fund ETF requires attention to detail. There’s already quite a few of these products trading, and more are coming. The strategies range from the exotic to the simple. Predictably, some are worthwhile, some aren’t. The first question for all of these funds: Is there any possibility for value-added management alpha? If the answer is “yes,” then the second question: Is the fee reasonable?