I would ignore the above advice. You cannot pick & choose between long term & short term holdings. Based on the legal precedents, your entire activity will be examined & judged. If short term transactions predominate (on one broker account/HIN), all of your activity will be judged as a business. If long term activity predominates (on a HIN), you will be judged as an investor.
If you wish to both trade & invest, I would recommend to open a 2nd broker account and have two accounts/two HINs. Use one account (example with E-Trade) for trading & use the other account (example with Commsec) for investing.
This, if necessary, will show the ATO you have two activities. Having two accounts is the safe way.
