Polystyrene products, like the "Polystyrene packing peanuts", are inexpensive and provide good drainage and air circulation. Many nurseries use polystyrene pieces to fill up pots and save on potting mix costs.

There are no advantages in using polystyrene as polystyrene does not contribute anything.

There are disadvantages:

a) It is very lightweight and makes pots with larger plants unstable.

b) It is biodegradable and will decompose. Decomposed polystyrene has no nutrients for plants.

c) Some chemicals used as pesticides or fungicides may dissolve it.