The latest ETF flow data shows an interesting split between Bitcoin and Ethereum, and I think it’s worth keeping an eye on.

U.S. spot Ethereum ETFs had a $2.81 million net outflow on September 29. This ended a seven-day inflow streak that had brought around $850.8 million into ETH funds. At nearly the same time, Bitcoin ETFs kept their buying streak going, bringing in $66.19 million and extending the positive run to nine sessions.

At first, this could look like a shift in institutional preference. But the data is a bit more complicated than that.

ETH Is Losing Momentum While BTC Keeps Attracting Capital

For me, the main point isn’t the single-day $2.81 million outflow from ETH. That number is pretty small.

The bigger thing is how quickly Ethereum’s flow momentum has slowed down.

The seven-day ETH streak brought in around $850.8 million, with the strongest day reaching $269.98 million on September 21. By September 28, daily inflows had already dropped to just $17.1 million, before turning negative the next day.

Bitcoin, meanwhile, has attracted roughly $3.08 billion during its nine-session inflow streak. That’s about 3.6 times the amount of capital Ethereum attracted during its latest seven-day run.

That difference is hard to ignore.

What I find interesting is that strong ETF demand hasn’t led to immediate price gains for either asset. ETH was down 3.32% over the week despite the large inflows, while BTC was down 3.78% during its own nine-session inflow streak.

So, ETF flows can be a strong demand signal, but they don’t always become an immediate short-term price catalyst.

Ethereum ETF inflow streak ends with outflow. Source: SoSoValue.com

Could Capital Rotate From ETH to BTC?

This is where the market narrative gets a little more interesting.

It would be easy to say that investors are selling Ethereum ETFs and moving that money into Bitcoin ETFs. But I don’t think the current data is enough to make that claim yet.

What we can say is that the relative flow picture is currently better for Bitcoin. Ethereum’s momentum has weakened quite a bit, while Bitcoin continues to absorb institutional capital. Recent reporting also shows that Bitcoin ETFs brought in billions of dollars during the month, while Ether’s 30-day inflows were roughly $982.5 million as of September 29.

For ETH, the main risk right now isn’t just one small outflow. It’s the possible change in marginal demand. If the next few sessions continue to show weak or negative ETF flows, traders may start seeing the recent $850.8 million inflow burst as a completed wave, instead of the start of a new accumulation trend.

For BTC, continued ETF buying could strengthen its position as the preferred institutional exposure to crypto. But there’s also an important caveat here. Bitcoin’s price has been relatively weak despite the inflows, which suggests ETF demand is being offset by other factors, including profit-taking and broader macro pressure.

Final Thoughts

My takeaway is fairly simple: the difference between the ETF flows deserves more attention than the single-day ETH outflow itself.

Ethereum still has meaningful institutional demand, and its U.S. spot ETFs hold around $17.79 billion in net assets. But the loss of momentum is happening while Bitcoin ETFs are still attracting a decent amount of capital.

From here, I would mainly watch three things:

• whether ETH ETF flows return to a sustained positive trend;
• whether Bitcoin can maintain its inflow streak, rather than just extending it with smaller daily numbers;
• and whether the growing flow gap starts leading to a wider performance gap between BTC and ETH.

For now, I see this less as a confirmed “Ethereum-to-Bitcoin rotation” and more as an early divergence in institutional demand. If that divergence continues, it could become a much more important market signal than today’s relatively small ETH outflow.