I have not heard about any specific instances where Black/Stippled clingfish (Gobiesox punctulatus) have become particularly aggressive. However, @Chasmodes had a closely related Skilletfish (Gobiesox strumosus) capture a juvenile blenny. Skilletfish grow about an inch longer than Stippled clingfish.Oh wow, I didn't know the black clingfish could be a potential issue. I thought they were supposed to be pretty peaceful and timid, I was considering getting one as well.