Questions about Aerogarden Setup

The search function isn't working for me, so I apologize if these questions were already stated before.

I just purchase a 12" airstone for my aerogarden, and it barely fits, right underneath the "fill up to here" point. Should I return the airstone for a smaller one, or will it do?

I was also wondering what other medium I can use if I don't have the Aerogarden sponges. I'm planning to buy clones from a clinic, and they always have their plants in rockwool, which is supposedly hell if you use an Aerogarden. I remember reading that foam works, but any specification would be much appreciated. Thanks!

If it was me I would get a 6" airstone. Thats what I have and it sits right at the bottom it only cost me $2 so it is worth getting. I have seen people on here using rockwool before but have no idea about any problems they had with it and I have also heard about using regular foam. You can also get a master kit with empty foam pieces.

I use rockwool and havent been havin probs or not yet anyway and im a month in