Dimensions are 36x18 on the bottom...maybe 19 deep. I think they'll be fine for quite some time. From what I've learned, they'll probably get to 8-10 inches in the first year or so, after that it'll be quite some time before/if they reach 12" long, by which point I'll almost certainly have a 4-5' tank to put them in.
And yeah the barbs are still alive...my JD doesn't seem to be too aggressive, although he is probably only 3" at this point, so we'll see what happens as he grows. Right now he just pecks at the bichirs once in a while and chases the convicts around. The barbs get 100% ignored by everything in the tank, and some them are less than inch still. So I'm not terribly worried about them.
I think the tank is going to work out fine for at least a year before I need to upgrade tanks or move anything around. They'll at least give me time to get into a house where I can afford to put another tank (if they know whats good for them

)