Wall Street’s notorious dark pools—private trading venues that allow investors to execute large stock transactions away from public exchanges—are becoming even more obscure. A decade after regulators cracked down on their lack of transparency, these off-exchange platforms are introducing “private rooms”, taking secrecy and exclusivity to a new level.
These gated trading venues, embedded within dark pools, restrict participation to a select group of traders. Unlike conventional dark pools, which anonymise participants but remain accessible to all eligible traders, private rooms allow firms to curate their own trading counterparties, creating a more controlled environment. While proponents argue that this fosters efficiency and minimises market impact, critics warn that it further fragments the stock market and reduces transparency.
The rise of private rooms
Dark pools have long attracted investors seeking to execute large trades without broadcasting their intentions to the broader market. The concern is that if a significant order becomes public knowledge, it can cause stock prices to move against the trader’s interests before execution is complete. Private rooms take this principle a step further, offering a bespoke trading experience where firms can choose exactly who they transact with.
“It’s like shopping when you know exactly what you want and who you’re buying from, instead of fighting crowds on Black Friday,” explains David Cannizzo, head of electronic trading at Raymond James & Associates.
While the exact number of private rooms remains unknown, industry insiders suggest their adoption is accelerating. Some dark pool operators report that private-room volumes are surpassing overall trading activity at smaller dark pools, highlighting the growing preference for customised liquidity pools over broader, anonymous exchanges.
Who’s using private rooms—and why?
The appeal of private rooms varies by market participant. Hedge funds, market makers, and asset managers are using them to execute trades more efficiently, avoiding interaction with counterparties who may exploit their trades. Broker-dealers also benefit by prioritising counterparties who align with their execution strategies.
For example, CastleOak Securities, a minority-owned brokerage firm, utilises a “diversity pool” provided by OneChronos, a dark pool operator. This room exclusively consists of minority-owned brokers, ensuring that trades occur within a community of firms with similar business objectives.
“It’s like an exclusive event where only invited guests can enter,” says Carlos Cabana, head of equity sales and trading at CastleOak. By using this model, CastleOak has significantly increased its trading volume with OneChronos, now ranking it as their third-largest trading venue after the New York Stock Exchange and Nasdaq.
Execution and market fairness
Private rooms operate under various names—hosted pools, ATS pools, custom counterparty groups—but the underlying principle remains the same: controlling who trades with whom. Brokers using these rooms typically execute trades at the midpoint of the National Best Bid and Offer (NBBO), ensuring fair pricing. If an order isn’t filled within a private room, it may still be routed to the wider ATS or public markets.
For traders, the appeal is avoiding toxic liquidity, where high-frequency traders exploit their orders. “The challenge is distinguishing good liquidity from bad liquidity,” explains Jatin Suryawanshi, global head of quant strategy at Jefferies. Private rooms provide a solution by letting firms prioritise preferred trading partners.
Regulatory uncertainty and market fragmentation
Not all dark pool operators have embraced private rooms. PureStream, another alternative trading system (ATS), offers sub-pools that function similarly but remain open to all subscribers rather than being restricted. CEO Armando Diaz questions whether private rooms blur the line between ATS and proprietary trading venues, raising concerns about regulatory oversight.
“The more control a host has over a room, the greater the regulatory risk,” warns Diaz.
Critics argue that private rooms contribute to “phantom liquidity”, where trading volumes appear robust but are, in reality, inaccessible to many market participants. Because dark pool operators lump private room trades into total reported activity, investors outside these rooms lack a clear picture of the market.
Although ATSs are regulated by the Securities and Exchange Commission (SEC), disclosure requirements are limited. While they must file ATS-N forms, which outline trading mechanisms, these documents do not specify how many private rooms exist or who is using them.
Larry Tabb, head of market structure at Bloomberg Intelligence, points out that regulators do not require ATSs to differentiate between dark pool and private room volumes, further obscuring market transparency. “There are no rules forcing ATSs to disclose the volume executed within private rooms versus open pools,” he notes.
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A growing trend?
Despite transparency concerns, private rooms are rapidly gaining traction. IntelligentCross, a major ATS operator, reports that private-room trading represents 5.4% of its overall volume—a figure expected to grow as firms adapt to these new trading mechanisms.
OneChronos CEO Vlad Khandros echoes this sentiment, stating that while private rooms currently account for less than 5% of total trading, demand is surging. “We’ve seen increased interest from both retail and institutional brokers,” he says.
Some firms are moving as much as 75% of their trading off-exchange, leveraging private rooms alongside dark pools and single-dealer platforms (SDPs). While major banks and brokers have the resources to create their own ATS or SDP, smaller firms rely on private rooms to compete more effectively without the burden of regulatory compliance.
The future of private rooms
As off-exchange trading continues to evolve, private rooms appear to be a permanent fixture in Wall Street’s financial ecosystem. They provide a compelling balance of secrecy, efficiency, and control, but their growing presence raises critical questions about fairness and market structure.
Are private rooms simply a natural evolution of dark pools, offering traders more efficient execution mechanisms? Or do they represent a dangerous step toward a two-tiered market, where those with the right connections enjoy an unfair advantage over retail and institutional investors alike?
For now, private rooms remain in “growth mode”, with increasing adoption across the industry. But as scrutiny builds, regulators may soon be forced to decide: how dark is too dark?
