between NY and AU session spread can unexpectedly be expanded in 10 times without any news!!! and will kill your profitable trade, I working with 2 brokers and only with FXCM I got this issue, so , I would recommend you to think at least twice before you will start to work. Spread working against your trade with this broker. From attached screenshot you can see how stop loss has been triggered on and the orders was filled with not the best available price on the market but just with some price proved by FXCM 'NDD' ? I showing screenshots from MT4 - FXCM and another global broker I working with, probably you can also check tick history taken from ECN brokers.
it's important to note that the spread widening you mentioned did not occur at some random time. It was due to trade rollover which occurs at 5pm New York time every weekday, so it's not unexpected like you are suggesting.
That is the time when one trading day ends, and the next one begins in the global forex market. Banks use this time to refresh their servers as they apply rollover interest to open positions. Some banks will widen their spreads around this time while others stop quoting prices altogether.
It's precisely because our prices are determined by what we receive from our liquidity providers, that spreads can widen accordingly at 5pm. As you can see from the tick chart above, this only lasts for a few minutes and is something you can prepare for by being flat at 5pm, or at least not trading with tight stops at that time.
It's worth remembering that on FXCM's No Dealing Desk (NDD) forex execution, whether your stop loss gets hit, or your take profit gets hit, we make the same amount of money from your trading volume, and we do not profit from your losses. In fact, it's in our best interests for you to be profitable, so you can continue trading with us.