Its not in the corners, if you would take the glass panels that make up the length of the tank. At the bottom where they connect with the bottom glass panel is where hes biting the silicone sealing. Its not deattached, falling apart, nor stringy. He runs his nose along the silicone and knows where the silicone sealing stops on the length wise and bottom panels of the tank. Then he starts biting it like its a prey whos hiding from him. I've never heard or seen this either. Its strange!