[ipv6ipv4]

These dark pools and private rooms appear to be a response to HFT. To get away from HFT. So HFT appears to be fragmenting the market which is probably not a net good. If that is not the purpose of dark pools and private rooms, then what other purposes do they have?

[bormaj]

One of the unique aspects of dark pools (and this can vary by venue) is that orders are segmented according to the source type (e.g. retail, client of the operator of the venue, institutional trader, etc) and the quality/grading of their order flow. As an institutional trader trying to leg into/out of a large position, you'll want many different execution options to help minimize price impact + information leakage + execution time. Dark pools are a great option in which you may have the option to specifically trade against non-toxic order flow (e.g. retail) to achieve better execution.

There are other reasons as well, but these venues essentially exist to solve some very niche problems for institutional trading. Public filings are available for review in case you're interested in the rules of each dark pool. [0]

[0](https://www.sec.gov/about/divisions-offices/division-trading...)