Just wanted to mention crowntail isn't really considered a short tail type. I have 3 male CTs and one of them is a chronic tail-biter. The other two have gorgeous long crowntails. Before I got the tailbiter I used to think that CTs didn't do that. LOL
I've just decided its more of a personality thing whether they end up biting or not. I have a halfmoon that has had a short tail since I shipped him from Thailand. I finally gave up trying to find the perfect home for him that would keep him from biting and figured thats just what he's going to do. Although I still keep him in a small (2 Gal) tank by himself.
As far as divided tanks I decided my favorite way is to do a "double divider". I have a tank that has two dividers with plants in the middle. the two guys that live on either side don't ever see their neighbor so they don't get stressed out. Here's a pic. Just an idea :)
This is kind of an old pic. The tank currently has a couple more plants stuffed in the middle section.