hey nick. it looks like you are the proud owner of a FICUS tree, which just happens to also be one of my favorites. i currently own 6. from the look of the pic i'd say the species is a banyan fig but all ficus pretty much have the same care. some basic care info on ficus. first and foremost, they can sometimes get fussy about being moved around and will drop their leaves. so if the tree drops it's leaves don't think it died on you. they are a tropical tree good for indoor bonsai and shouldn't be exposed to temps below 50F. they perfer moderate indirect light but will be forgiving for some varience. mine get full sun for about 2 hours and then indirect for the remainder of the day. i tend to water mine 2 times a week so they don't dry out to much but you don't want them or any bonsai constantly soaked wet or they'll get root rot, i also give my trees a light misting with a spray bottle but this should be done early in the day to avoid light scorching the leaves. your tree looks to be styled in informal upright (bending trunk) you can use copper wire to change the direction of the canopy branches (perhaps pull the downward a little) but trying to change the trunk at this point would be a more advanced practice. you can also prune the ends of the branches off so the tree will start new buds thus filling out the canopy more. one interesting thing about banyan figs is that the develope aerial roots as they get older. oh also before i forget that mushy green stuff is probably moss growing on the soil. it's more for a pleasing look but also does a good job holding in moisture. about repotting it, you'd want to look for tropical bonsai soil mix. you can find it and some nice pots on bonsaioutlet.com, a site affiliated with this website. however when repotting you want to keep as much of the original soil around the rootball intact as you can and judging by the size of your tree wihich you said was in a 6 inch pot and at this time i wouldn't put it in a bigger pot. i'd honestly keep it in the pot it's in now. traditionally unglazed pots such as this are used for non-flowering plants such as your tree. any other questions just ask. this site loves them and mark the administrator is always a big help. and P.S. if you look at my profile pic it's a pic of my banyan tree the same species as yours.