BlackRock's Bitcoin ETF Buys $1.08 Billion in 20 Days While Grayscale's Fund Sheds $255 Million

BlackRock's iShares Bitcoin Trust (IBIT) has taken in roughly $1.08 billion in net Bitcoin purchases over the past 20 trading days, according to on-chain data from Arkham Intelligence reported by PANews and Crypto Briefing. Grayscale's Bitcoin Trust (GBTC) went the other way over that same stretch, shedding about $254.7 million.

IBIT charges a 0.25% annual fee. GBTC charges 1.5%. On a $10 million position, that's $25,000 a year versus $150,000 for the same underlying exposure to the same asset. Grayscale has rolled out a lower-fee Bitcoin Mini Trust to compete, but the flagship GBTC product keeps bleeding money regardless.

The scale of the divergence shows up in total holdings. IBIT now holds approximately 785,000 BTC with assets under management above $60 billion, per Crypto Briefing's read of the Arkham data. GBTC holds roughly 130,000 BTC with AUM near $10 billion. Across all US spot Bitcoin ETFs, holdings now top 1.28 million BTC, about 6% of Bitcoin's entire circulating supply.

A rough week that didn't stop the trend

The 20-day BlackRock haul comes right after the broader Bitcoin ETF category posted its worst week since July. US spot Bitcoin ETFs recorded $462.7 million in net outflows across four sessions from September 8 to 11, according to Farside Investors data cited by FXStreet and Crowdfund Insider, snapping a three-week inflow streak.

Thursday, September 10 was the worst single day, with $282.7 million pulled out, the largest daily outflow since July according to FXStreet. ARK 21Shares' ARKB led the week's redemptions with $234.2 million, and Grayscale's GBTC followed. Here the sources don't fully agree: FXStreet and Crowdfund Insider, both citing Farside Investors, put GBTC's weekly outflow at $129.1 million, while Blockhead reported GBTC shed $156.3 million across the same four sessions. The roughly $27 million gap likely reflects different data providers or cutoff times, but neither source ties the discrepancy to anything beyond routine reporting variance.

Even IBIT posted red ink that week, though a comparatively small $52.5 million in net outflows versus the hundreds of millions leaving ARKB and GBTC, according to FXStreet. Despite the reversal, Bitcoin ETFs stayed net positive for September overall, with roughly $307.3 million in cumulative inflows through September 12.

BlackRock's outsized share of every good day

On August 27, IBIT alone pulled in $277.6 million while the entire US Bitcoin ETF market gained $242.3 million that day, according to CryptoSlate's analysis of Farside data. That means IBIT's single-day haul exceeded the market's total net result by about 15%, with Fidelity's FBTC and Grayscale's GBTC losing a combined $110.8 million the same session.

Over the nine-day inflow streak that ran from August 17 through early September, IBIT supplied about $2.3 billion of the roughly $3.05 billion the category attracted, or 75.6% of the total, per CryptoSlate. IBIT became the fastest ETF on record to hit $50 billion in assets, doing so in about 11 months after its January 2024 launch.

Ethereum ETFs have moved in the opposite direction from Bitcoin funds lately. They pulled in nearly $197 million during the same September 8-11 stretch that saw Bitcoin funds bleed, extending Ether's inflow streak to four straight weeks, according to FXStreet and Blockhead. BlackRock's iShares Ethereum Trust led that charge with $148.8 million on Friday, September 11 alone.

BlackRock's concentration of Bitcoin ETF assets

BlackRock's growing share of Bitcoin ETF assets raises a fair question: does one firm holding roughly 785,000 BTC and supplying three-quarters of the category's net new money in recent inflow streaks concentrate custody and liquidity risk in a single institution? No source here alleges regulatory concern or misconduct, and no investigation has been announced. BlackRock's scale advantage, a $10 trillion global asset base and existing wealth-management distribution, is the plain explanation multiple outlets give for why advisors and institutions default to IBIT over competitors with functionally identical exposure to the same asset.

Bitcoin itself traded near $77,500 to $78,000 in recent sessions, according to CoinGecko data cited by Blockhead, after rallying from around $62,000 in mid-August. That backdrop sits alongside two catalysts landing this week: a Senate cloture vote on the CLARITY Act scheduled for today, Tuesday, September 15, following a revised draft with an ethics provision reportedly backed by President Trump, and the Federal Reserve's policy decision scheduled for Wednesday, September 16. Polymarket was pricing the bill's odds of becoming law at 31% as of the revised weekend draft, per Blockhead. Whether Wednesday's Fed decision reverses last week's outflow pattern or accelerates it is still an open question the flow data hasn't answered yet.