Bobby, please read my post above one more time. ELP was a BUYER on this trade. So "someone" sent a SELL order at the same price as you did, but instead of posting it on the book someone choose to route it to ELPs. You could have done the same.
ROUZ, if routed to dark liquidity, will charge how much? I have this route and haven't used it. It sounds like when I send an order to EDGA it's advantageous to use ROUZ to have access to more free liquidity. Explaining this would be GREATLY appreciated, thanks.