Dark pools in the United Kingdom need to be more transparent, and traders need to have a clear understanding of the benefits they’re receiving from trading in the dark, says a thematic review published Thursday by Financial Conduct Authority (FCA).

The review, which looks at dark pools efforts to deal with conflicts of interest, their governance, oversight and controls, finds that the firms operating dark pools “have made significant progress” in addressing conflicts, but that more needs to be done.

Dark pool operators should be doing more to identify and manage conflicts, the FCA review says, including strengthening their policies and procedures for oversight, and regularly undertaking independent assessments.

Additionally, it says that these trading venues should be providing, “clear detail about the design and operation of a dark pool to users and, for investment banks, this includes describing precisely how their broker crossing network interacts with other components of their electronic trading platform.”

The review also calls for dark pools to improve the monitoring of the trading activity that takes place in their pools “with a focus on operational integrity, best execution, client preferences and unwanted trading activity including market abuse.”

For traders that utilize dark pools, the FCA review says that they should be “very clear about the rationale for using dark pools,” they should conduct sufficient due diligence on the operating model of each dark pool they access, and they could improve their monitoring of results versus expectations when using dark pools.

“It is vital that we have clean, effective and competitive wholesale financial markets. This review aims to address concerns about the operation of dark pools in the U.K.,” says Andrew Bailey, chief executive of the FCA, in a statement.

“Advances in technology have had a huge impact on equity markets which, in turn, give rise to new forms of conduct risk. Similar changes are underway across other products and markets so it is important for boards and senior management to read across, and apply what they have already learned, to rapid changes occurring elsewhere,” he adds.

The FCA calls on both dark pools and the traders that use them to consider the findings of its review, and says that it will seek action to address areas of concern.