My indo is a foot long and doesn't bother my fire eel, juvie sleeper goby, gars, or my 8" suncat. He gets grumpy when my big marbled pim sits on him but he just rams him or nips him gently and chases him off. I doubt he'd bother bichirs. He only gets grumpy if someone bothers him. He used to pick on and chase our breeding sevs because they'd harrass him and try to chase him out of their territory, but he never injured them severely. Just shredded fins. I removed them mainly because I didn't like them aggravating him.
Stable and unstable just refers to the clarity of the pattern. Clear well defined stripes on a solid lighter background is stable. A fish that turns dark, has faded or "choppy" stripes that blend more into the background is unstable.
Dats usually don't stay vividly and clearly patterned until they get a certain size, and many as adults won't stay that way all the time.
A stable dat is considered more attractive and possibly more comfortable with his surrounding. It really doesn't indicate anything about the health of the fish, since some big healthy dats don't stay stable. It's personal preference, and some people don't care either way.
