BlackRock updated its Bitcoin ETF plans and added big Wall Street firms like Goldman Sachs and Citigroup.

These firms, called authorized participants, help create and redeem shares of the ETF.

The SEC wants to prevent market manipulation in Bitcoin ETFs, so it prefers cash transactions over direct asset handling.

BlackRock and other big companies are following the SEC's guidance and using cash transactions in their ETF filings.

Bitcoin ETFs had a busy March with $111 billion in trading volume, but there are signs that demand might be slowing down.

BlackRock's Bitcoin trust is the most popular, with $17.6 billion in assets as of April 1st.