Join Date: Sep 2012
Location: Okanagan Valley, BC, Canada
I am not expert, but my male molly did the same. I think I have it figured out. Depending on which lights are on in the room he can see his reflection and competes with himself. It's an equal battle, so he never wins and doesn't stop. If I change the room lighting he doesn't get the reflection and he stops racing back and forth.
I don't know if that applies to you, but I thought I would mention it in case it helps. For me it was a simple thing to fix, but took me a while to figure out.