Trading in US with IB - tax in AUS?

Hi

I just opened an account with IB to trade US stocks, AUD as base currency...

Can anybody please explain to me tax responsibilities ?

If I keep the money in my IB account (USD), do I still need to declare gains in my AUS tax return ? or only when I move it back to AUS currency is it considered a realized gain ? can anyone point me to a link with an explanation on how to treat USD gains for tax purposes ?

thanks

a.