Quote from ianjohnson:
Personal experience here as a model trader/ECN connectivity guy at both a hedge fund AND bank, including Hotspot, Currenex, Lava, SpotAi, AutoQuote, eSpeed ....
Banks will generally throw you out if they can't hedge your deal consistently, especially if you start jacking up the amounts. They also get upset by consistent out trades. I don't believe bank look at any pair of trades as predatory unless they feel like they are being drawn consistently into a poor position. As long as they can hedge at a profits, they'll love you.
HotspotFX executes fairly quickly and consistently but are quick to throw you out - Scalping is unlikely in itself to get you thrown out - more dangerous are take out/sniping models.
Currenex bank streamers employ last look protection to hold onto the execution, possibly until the market suits them (or to bitter the taste to persistent offenders) - Expect fill times in the seconds, even for IOC orders. Not so likely to switch off because this