what would be a good soil for this?
Opening 'soil-can-of-worms' ..
A good mix for tropicals is 1/8-1/4" lava rock and some humus .. with less humus if you tree will see cooler (40-50F) periods in the winter.. more if it is going to be sitting in full sun during the summer.
I've grown in straight lava with great results. i was unable to get it in large quantities and had to use other materials like turface(high fired clay 1/8-1/16") .. screened and sized granite paver base..
high fired shale.. chicken grit.. turkey grit.. while in TN i sieved the coarse sand and small rocks from a creek.
Soil mix is a personal thing.. what are you growing conditions? what ingredients are available in your area? how large is the container? how much soil do you need? what are your watering techniques?
but i feel the main premise is to have a mix which drains well.. the coarse particles the same size.
Enough humus to hold water for moist not soggy conditions.
There are suppliers with pre mixed bonsai soil or you can get ingredients and do it yourself.
I like lava rock because it hold moisture and traps oxygen in the soil which helps create feeder roots.. root tip hit oxygen and split.. creating many feeder and less heavy roots.
How is your mix doing? does it absorb the water readily? does it drain well?
I probably wouldn't repot for a couple yrs. Let it get some growth up top and then move it into another mix.
Season Greetings.. and Hopes for a Peaceful 2010 ...