I've been successfully scalping low liquidity stocks/ETFs (not penny stocks) with IB TWS for about a year and a half. I use Scottrade streamer to get my T&S info. I always have lots of non-marketable limit orders and am frequently on the inside of the advertised spreads. I lose a lot of liquidity to hidden orders which are a fraction of a cent inside my order. I see lots of executions occuring at these prices. Who are these traders and how can I compete with them? I get an error when I try to place fractional cent stock orders with IB TWS. Is there a method using my IB account or another broker who will let me place fractional cent hidden stock orders just inside the NBBO so that I'm more competitive?