Your corals sound great. They are fast growers though, so be prepared to do some pruning in that little tank. I don't know a lot about that specific goby, but I don't think it is a shrimp goby. I would also be careful if you buy a second one to pair with it. Unless they are a mated pair, they will probably fight. I had two neon blue gobies in a 55. I got them both at the same time when they were small. I hoped they would pair but instead one grew significantly larger and constantly harasses the smaller one. And this was in a 4' long tank. It would be even worse in a nano. If you would like to add another fish I would go with a true shrimp goby and pistol shrimp. Otherwise you could go with any other small goby and the fire shrimp. If you want to continue to use a power filter, the penguin and emporer ones are pretty good. Just don't use the bio wheel. Also be sure to rinse out the filter pads every week or two. I would use b-ionic or c-balance in there but very very small quantities. Your corals will not take up much calcium, but you still need to maintain good calcium to alkalinity ratios. If you are doing weekly water changes, however, you might not need to do this. Just test your water regularly and if your ca/alk remain stable you're good to go.
