I dont know exactly which goby I have, but I do know that its a sand sifter. It has a white body with some neon blue speckles on its gills. I've had him for about 2 months and hes starting to thin up a lot. He wont eat brine, pellets, flakes, nothing. He gulps em up then shoots em back out through his gills. Any ideas what I could/should do? Thanks!