Science Buddies: "Ask an Expert"

Hi,

I'm making a mini cactus terrarium in my own time similar to this image here (wouldn't let me attach file): https://snipboard.io/qyHUpT.jpg

I'm looking to turn it into a little necklace.

I was just wondering would anyone have any idea what is being used in the base, because I don't want it to be soil but it looks like its something else. Or any suggestions on what could be used? It needs to be something that will hopefully allow the cactus to stay alive and grow but not grow really fast, and make it easy to water - such as soaking the base in water.

Any answers are much appreciated!

Cheers

Hello. Is this related to a science fair project? This forum is focused on helping students with their science fair project.

If so, tell us more about your project. If not, there are other forums more appropriate for this discussion.

Thanks!