As already stated, they should do fine together. I have both of them aswell, in my tank. No issues here. Im not sure, though, if you were asking this assuming they both eat copepods. I dont know that a diamond sided goby eats copepods, not that they are against eating them, but I dont think they feed on them as the majority of their diet. Mine eats any frozen foods I put in the tank and he is a pig. Also make sure your rocks are pretty stable. These goby love to move sand all day long. Creating caves and caverns that he sits in. Mine also will swim like he is a normal fish, not just a sand dweller.