SYBA Soil - Activated carbon
Activated carbon pellets (also known as activated charcoal) filter out any harmful chemicals, metals, mould and other nasty things you don't want in your terrarium or houseplant soil. Add it just above the drainage layer of your terrarium or mix it into your plant soil to filter out the bad stuff.
The carbon also works great in aquarium filtration. They come in convenient and resealable bags. 
  Mold will be a thing of the past
  Odour prevention 
  100x surface area compared to charcoal
One main benefit is the reduction of nasty smells, this works for plants, terrariums & aquariums.
The benefits of activated carbon for terrariums
By adding activated carbon to the soil you are protecting the root system against possible pests & moulds. While it isn’t 100% protection, it does offer an extra safety barrier. It also creates a more gritty & airy texture preventing too much moisture in the soil.
The benefits of activated carbon for plants
In terrariums we add activated carbon both in the soil mix and the drainage layer, this way the water is being pushed through the charcoal every “cycle”, maximizing its effects. We have done many tests on identical terrariums with the only difference being the addition of carbon, and the reduction of mould growth is insane. 
What makes carbon “activated"?
By treating regular carbon/charcoal with high temperatures, they expand. This creates lots of tiny air pockets. These pockets create the basis for the adsorption potential of the carbon, making it about 100x more effective (more surface area) than regular charcoal.