I've kept a couple of these animals over the years... Would still have two of them if it weren't for my plumbing mistakes...
Anyways's at one point, I had a Mertensii Carpet, a Sebae, and 2 E. Quad clone's in a 55 gallon tank. They all got along just ducky. Then the great flood of 2000 came, and I lost the Sebae and Carpet. Now I have 2 (maybe 3, can't tell) clones of my original E. Quad, and a Rose E. Quad in my 90... Nary a problem. The E. Quads are pretty far apart, however.
My Carpet and Sebae came VERY close to touching for several months, but for some reason, they never "went at it" with each other. The Rose started out it's life in my tank just below my E. Quads, and gradually migrated above and to the left. They have never been closer than those few inches away that I first placed them.
I may be interested in trading a Clone of my Normal E. Quad if you like, but there's a long line for Rose Clone's....

I can provide you with some pics, if interested PM me.
- Mac