U.S. spot Bitcoin ETFs recorded $433 million in net inflows on Friday, Sept. 18, led by Fidelity's FBTC with $311 million. Despite the strong daily showing, overall ETF holdings still fell by roughly 5,700 BTC across two consecutive negative weeks. Analyst Darkfost noted that Friday's robust ETF activity failed to reverse a second straight negative week. Spot Ethereum ETFs also posted positive flows that day, drawing $144 million in net inflows, with BlackRock's ETHA contributing $114 million, according to SosoValue.

Strong Friday Fails to Reverse Weekly Decline

According to Darkfost, Bitcoin ETF holdings lost approximately 5,700 BTC over the latest two negative weeks. He linked the trend to pessimistic news involving rate hikes and conflicts. These daily figures are closely watched because spot Bitcoin ETFs hold Bitcoin directly and trade on U.S. exchanges, making their net flows a running measure of capital moving into or out of Bitcoin through regulated vehicles.

Friday nonetheless brought a pickup in ETF activity. SosoValue reported $433 million in total net inflows for U.S. spot Bitcoin ETFs on Sept. 18. Fidelity's FBTC led the group with $311 million, while BlackRock's IBIT recorded $108 million.

Ethereum products shared in the momentum. SosoValue logged $144 million in net inflows for spot Ethereum ETFs, with BlackRock's ETHA accounting for $114 million and Fidelity's FETH adding $26.2449 million. Those Ethereum products began trading in July 2024, several months after their Bitcoin counterparts.

Flow Pattern Since January 2024

The latest figures fit the broader ETF flow pattern visible on Coinglass from January 2024 through September 2026, where green bars mark daily inflows, red bars represent outflows, and a gold line tracks Bitcoin's price. That window covers the products' full trading history, since the U.S. Securities and Exchange Commission approved the first spot Bitcoin ETFs in January 2024 and the funds began trading that month.

Early 2024 produced mixed ETF flows, with several inflow spikes nearing $1 billion, while outflows also emerged as Bitcoin traded with weaker price action through mid-2024. The pattern shifted from October 2024 into early 2025, when multiple inflow spikes exceeded $1 billion, with the largest reaching roughly $1.3 billion to $1.4 billion.

From mid-2025 through late 2025, Bitcoin showed stronger price action, and ETF inflows repeatedly ranged from $500 million to $1 billion. Outflows later increased, including withdrawals of approximately $500 million to $1 billion.

Mixed Flows Persist Into 2026

Entering 2026, ETF flows continued to alternate between inflows and outflows. Some green bars exceeded $500 million, although red bars repeatedly interrupted the pattern. Inflows became more visible again toward the chart's latest readings, yet the overall flow pattern remained mixed.

Darkfost said Bitcoin still delivered a solid performance during the latest week despite the decline in ETF holdings. Sept. 18 data underscored that strength, showing robust daily inflows across both Bitcoin and Ethereum spot ETFs. Upcoming daily flow reports from SosoValue and Coinglass will indicate whether the two-week decline in ETF holdings extends or reverses.