Sam, 2 things.
1 - SLV is a very liquid ETF and had 309,137 shares trade at the opening auction today. You are not going to have an issue with this ETF.
2 - The issue will come into play for illiquid ETFs with little or no opening auction volume. The greater the percentage of volume your order for the opening auction is, the greater the influence it will have on the opening price. PALL only traded 1,976 shares at the auction at a price of 210.81, which was above the ask price of 209.87 at the time.
There is no reason not to always use a limit order. It won't affect the price you order trades at but will prevent you from getting a fill at a price you don't want.
1 - SLV is a very liquid ETF and had 309,137 shares trade at the opening auction today. You are not going to have an issue with this ETF.
2 - The issue will come into play for illiquid ETFs with little or no opening auction volume. The greater the percentage of volume your order for the opening auction is, the greater the influence it will have on the opening price. PALL only traded 1,976 shares at the auction at a price of 210.81, which was above the ask price of 209.87 at the time.
There is no reason not to always use a limit order. It won't affect the price you order trades at but will prevent you from getting a fill at a price you don't want.