Pimco manages $3.4 billion globally in 18 ETFs, including seven that are actively managed. In the U.S., Pimco has four actively managed ETFs. Expense ratios for Pimco's four actively managed U.S. ETFs range from 0.35 percent to 0.45 percent, according to the firm's website.
So far, Pimco's actively managed ETFs have focused on highly liquid markets, such as Treasuries, where other investors mimicking the trades are less likely to affect prices. Fixed- income investments are also more difficult to copy because transactions don't occur on an open exchange.
Pimco wasn't very concerned that traders would try to mimic Gross's trades because his management style involves using a "risk-based approach," allowing him to use a range of securities to achieve his investments goals, Arnold said.
"It is more of a concern in the active-equity space," Arnold said.
Pimco Total Return Exchange-Traded Fund will trade under the ticker symbol TRXT, the firm said in April.