You are going to be pretty full at that point mainly because of the clowns and wrasses. The goby and RG will have only a small effect on your bioload. If you wanted anything else in the tank, I would suggest it be another goby or a firefish or something that is not a messy eater with a high metabolism. The RG will actually help to keep the tanks potential nuisances, like bristle worms, under control and would be a great addition. Another potentially good choice would be a mandarin goby, but your system needs to be up and running for at the very least, 6 months though I recommend a year before you try to keep one. What kind of skimmer are you using?