BlackRock Bitcoin ETF marks first day of outflow amid record-breaking ETF dollar outflows. The US-based Spot Bitcoin exchange-traded fund (ETF) posted record net outflows, and BlackRock's iShares Bitcoin Trust also posted its first-ever single-day outflow. According to Farside Investors, $36.9 million was outflowed from BlackRock's $57,786 Bitcoin BTC fund on May 1st.