I did quite a bit of research on the tailspot before I bought him & found that they like Ocean Nutrition Formula 2 flakes. My goby will also eat the flakes. Some gobies are quite shy & don't expect to see much of a change with the hiding until they are settled in. Sometimes it just depends on the fish's personality too.
My goby will eat frozen mysis & seems to eat whatever I feed the tank, flake or frozen. I throw in a small piece of sinking algae wafer, less than a quarter of the wafer, twice a week for the pistol & I have seen the goby grab the entire piece & take off for the burrow.
It took me 2 weeks before I saw the goby on a regular basis & was worried that I would lose it. I think they were out foraging at night while the lights were out & the tailspot was sleeping.