How to Re-pot a Moth Orchid Phalaenopsis
Use a proprietary bark-based orchid compost, to ensure good drainage and aeration of the roots. Carefully remove the orchid from its pot, trim off any dead roots (those that are dark brown and shrivelled) and old compost. Carefully hold the plant in the pot at the right level and gently add fresh orchid compost, making sure you firm it so that the orchid stays upright.
Do not bury any aerial roots as this can make them rot. You may need to use a cane to support the plant until it becomes established. Water well and allow excess to drain away.