Is there anyway to safely add a Diamond Goby in this situation

[Thanos]

I have an established ~2.5 year old 65 gallon reef with a 4 inch deep sand bed, and have been running into some issues with keeping it clean. For the first year and a half I had a diamond watchman goby, which pretty much single-handedly kept the sandbed spotless, but unfortunately he found a tiny gap in the top of the aquarium and launched his way through it one night. I tried replacing him with a new one and it went horribly. I had added a tomini tang after the original diamond goby with the intention of it being the last fish, and while those two got along very well and even shared a cave, the tomini tang relentlessly harassed the new one to the point of starvation; it was a night and day difference and the goby was pretty much trapped in the back corner of the tank for its entire time alive. I really want to get back to that picturesque white sandbed I had, but I don't want to send another diamond goby to its death. Is there any way to try and stop the tang from being super territorial to new fish or is my only real option to catch and sell the tang?

 

[SnazzyUrchin792]

I put a banded sleeper goby in a tank with a damsel, and when the damsel went to attack the goby the goby bit him. I don’t know if my goby is just bold, or if all the banded sleepers are like that. I also have a tang, and the damsel and tang both routinely fight the goby for its cave. Both fish already have other hiding spots, so I don’t understand the deal with this cave, but the goby always wins.

 

[Dread Pirate Dave]

You could try and put a divider in so the tang can grow accustomed to the new fish.