Soil lifespan?

[aquanatix]

Would like to ask your opinion regarding soil life.
How long should we wait before changing soil?
In my case of GEX...just how old is old or deemed "unsuitable" for planting?

[tawauboy]

it depends on the plants that you have.
if you find that they are not growing well, you may consider replacing the substrate. otherwise, you can insert fertilizer sticks.