Great orchids for Sydney, you can buy Phalaenopsis as a flowering display that will last for over a month, then keep them with an expectation that they will flower again. They are easy to keep as long as the basic conditions are right, and that means light and water.
Phals are low light plants, naturally growing deep under the rainforest canopy. Their thick leaves easily overheat in sunlight, even morning sun in Summer. A south facing window or a spot inside a brightly lit room are good locations. If you have a good African violet spot it will be good for Phals.
They also have remarkably low water needs. Their thick roots only contact the potting medium for support, and they don’t suffer from drying out the way most plant roots do. They also absolutely need airflow to avoid rotting. A weekly watering is fine, and the pots should never sit in water. Too little water will show as wrinkled leaves.
Summer temperatures are fine in Sydney, but there is a risk of chilling in winter. Seven degrees is about the damage level, and 10″C is a practical low limit to prevent leaf damage. I bring mine indoors for the (3) Winter months. In cold climates, inside with central heating is fine. I kept mine just fine in Switzerland, although re-flowering is less frequent there. Heated houses do tend to have dry air, so watch for wrinkles.
Officially, Phals need a cool period to initiate flowering, say nights of 12 – 15″C. In Sydney they are most likely to send up a new spike in May. They also flower from the spent flower spikes, so if you don’t mind the look, only trim the spike to where it dies back after flowering. I get these new buds at any time, but typically in February.
They don’t need repotting until the mix is degraded or there is trouble with the roots. I like to repot them into wide shallow terra cotta pots, but I’m not sure these are any better than standard plastic. The easiest mix is probably a standard bark one. Lift the plant away from its old mix and shake it away gently. Trim off any dead roots. Put the orchid in the empty pot and shake in new mix. As you see from the way new roots grow, they don’t actually have to all be in the potting mix, but the plants look neater with them tucked in the pot. The roots are in fact photosynthetic, and some growers prefer clear plastic pots which encourage the roots to stay inside.
Fertilizing needs to be dilute, but can be as frequent as you like. A half-strength soluble fertilizer watering once every month or two is fine, or if you really want to move them along you could water every time with quarter strength.
