Of course. As long as it's something that they won't hurt themselves on if they run into it or brush by.
SwayLocks, I don't think using a clear divider would take away ALL their aggressive tendencies, just the ones towards each other. They'll still flare at other fish if you let them see each other. And actually, I've heard that if you house two males next to each other (in say, side-by-side bowls), while they'll lose interest, you can put a piece of cardboard between them for a day or two and they'll start flaring again when you take it away.