I have a bi-color blenny, and when I first got my lawnmower they fought a lot. It took almost 2 weeks before they settled down and accepted each other. Now sometimes I get to see them perch on the same rock together. I had a second tank set-up so that when my bi-color started acting so territorial I moved him for a few days. When I put him back into my main tank there wasn't nearly as much problem between the two.