https://darkpoolsecrets.com keeps running ads on Fox Business TV offering a free book & DVD. It may be useless, but might be interesting or even good. I haven't read it. If you read it, come back and share your review.
Research for yourself, but: I believe they are reported on the Tape ... just delayed. I believe software/services exist that will monitor the tape for such out-of-sequence trades ... or you can do it yourself (automated or otherwise).
I am thinking that volume from the dark pools has to appear in the stockmarket for that security. They have been trying to hide trading volume for sometime. I remember Martha Stewart and her MSO stock was going up as she was locked up for insider trading. Remember that? Well, her transactions came up on insider trading stats with orders of 1,000, 2,000, 4,000 lots placed over and over. You have to figure out that she was dumping her stock as it was going up! Those transactions reported to the SEC! Of course, the dark pool, you do not see it right away but, I would guess it will be added to that day's volume somehow. So, the stockcharts and volume probably, will give clues.