Foulthrow, many stocks on the ASX are traded by algos bots that...

Foulthrow, many stocks on the ASX are traded by algos bots that the ASX and alternative exchanges allow to operate, its not just an AU thing it happens all day every day in UK, US etc markets.

The Algo can be set on any number of pre sets but for your example there may well be two algos running one for a buyer and the other for a seller, or indeed someone doing either buying or selling that 'supports' the other side of the trade in order to present a scene that suggests demand or supply that is not actually there.

Some of these algos 'sniff' orders coming down the pipe and will react accordingly ahead of your order getting to the platform so as to not get hit if it is the side of the trade they are not interested in.

Any of this make sense? Happy to try and explain more if required.