I used a mix I bought at a bonsai nursery that was near me, sadly closed now. It was labeled "tropical bonsai soil". The only difference really was a bit of pine bark I think. They aren't that particular if they are watered correctly. Best of luck with yours, they are fun trees.Your trees are beautiful. I have a few questions but I wondered what substrate you use on your Barbados Cherry. Is there are a premixed soil that you use or what do you recommend? We just got a pre-bonsai Barbados cherry that's only a few years old and will stay in dirt for another year to thicken the trunk but any suggestion would be appreciated. Thank you, Katie