Can't exactly tell from the picture, but it looks finer than mine (mine is around ~1mm grain). Do you have a powerhead? With or without the goby, sugar fine sand proves to be an issue if you're constantly dealing with cloudy water. In my opinion, your tank doesn't look particularly cloudy so I would bite the bullet and care for the goby until the end of its days. Seeing that you're just now having an issue with cloudy water, I wouldn't worry about the sand unless you haven't had any sort of aeration or flow in the tank before.
At the end of the day, it's your call. Monitor the goby's behavior, be patient. As someone else mentioned, it may slow down as it gets used to your tank. If nothing changes, perhaps invest in a cute little snail! : )