Starry Blenny always seems mad

[ZzyzxRiver]

I’ve had a starry blenny and a blackcap bass both coexisting peacefully in my 50g tank for at least six months. Recently my blackcap started building a nest in a cave, and after that the two of them started beefing. It’s mostly what I assume are dominance displays, not any physical attacks yet. The blenny is frequently flashing white:

I think the aggression is also partially because both are getting bigger. But is this a health issue for the blenny, or is he just surly and this’ll be part of the dynamic of the tank? He attacks my hand and any tools that come into the tank, but is totally fine with all the other fish.

 

[Uncle99]

They are a good combination as they utilize different parts of the rock work and your tank is rightly sized.

But the Black Cap is still territorial and will defend its cave.

That being said, I would expect the displayed aggression may occur if the Blennie gets to close, but, the Black Cap is not going to seek out trouble and is just a show of “this spot taken”.