Curious if anyone has put a Lawnmower / Algae blenny into a smallish tank (20g) with a watchman goby. I had a bicolor blenny in there. The goby and the bicolor beat the fins off of each other. I finally had to separate. Based on that experiment, I'm leery of adding the Lawnmower to my otherwise peaceful tank.
Bi-colors are the more agressive of blennies IME-Tail spot blennies are sweet! I have one in my 8g along with my FireFish-Prawn and Tangaroa gobies. No aggressive behavior at all! Not sure if this helps you at all
I'm a big fan of orange spot gobies, or any of the gobies that will clean the sand. I had one and a lawnmower in a 29G nano a few years ago and they got along just fine. They both got transferred to the 75G tank when it arrived, and are fine in there too. The issues I have with them involve making sure all of the corals are up on rocks so the goby can't bury them, and gluing everything down tight so the blenny can't knock the corals into the sand so the goby can bury them. I've had a few corals 'disappear' that way.
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