Territorial Tailspot Blenny

[EmmettPeck]

Hey all, I have a 20g cube with an aquascape of caves and passages and two fish inhabitants of 4 months, a tailspot blenny and a yellow watchman goby. They were added at the same time, and were on good terms until about two months ago when the tailspot began to lunge at the goby when the goby neared their den. Since, this has progressed to chasing on sight and now into actively seeking out the goby, moving dens to one high up with a vantage point.

Realizing the stress on my goby, I added a pistol shrimp to accompany them as the goby spent most of their time in various caves, looking out for passing food. Since the shrimp was added, they have dug out a large cave under one of my rocks and I have only briefly seen my goby, often before or after lights are on/off peeking out from the den.

Does anyone have any tips to improve the aggression in my tank? I feed plenty of food, if anything the blenny is just such a chonky lad that he wishes he could keep all of the food for himself despite being completely full from algae in a day. Should I consider adding a 3rd, larger fish to adjust dynamics, or is this a terrible idea? Pair of clowns?

 

[mann1139]

You can try moving the rock around. Sometimes that resets aggression.

Third fish may help, or may make it worse.

 

[EmmettPeck]

Sadly Tailspot blenny is still at it, poor guys have been under the same rock for a few days.

I'm considering constructing an acrylic cage to "divide" the tank, mostly just provide a large space for the pistol shrimp to tunnel into that the tailspot cannot otherwise enter. Hoping this divide reestablishes territory. I'll keep this thread updated!