Yes!!! That looks so cool! Glad you went with some bar gobies! Yeah, I haven't had any issues adding more bar gobies after the fact. I have added one or two to established shoals of 5-6 and they don't really seem to care.We started with 30 Zebra Bar Gobies. Nice little school for now. Were going to add to it or start a school of blue green chromis.
I could be wrong, but I think they will be compatible with other types of dartfish like the scissortail or blue gudgeon, so you might be able to get those as well. They might shoal separately, but I believe they wouldn't fight with one another (I would look into it though)
Also a fish idea that aren't shoaling fish would be a male/female pair of bluethroat triggers (completely reef safe)
Sorry had to mention it since that's one of my favorite fish that I cannot keep yet due to not having a big enough tank.