I know this thread is dead. Just wanted to let people know that forex arbitrage is heavily frowned upon. If your broker allows it chances are you are not going to make money doing it because of spreads and trading costs. If you somehow get over that issue and start making money, they will shut you down because arbitrage is considered toxic flow. It hurts your broker's relationships with the banks.
Don't do it. I tried.
For the most part, this is true. However, this is because most traders are greedy and try to extract every last 1/10. They want tight spreads, no last look, etc.
But... there are ways to do it that are deemed friendly but you have to know how to structure it.
and of course HFT programs that can hook up to multiple LPs thru their PB are actually encouraged if structured properly.