Diamond Goby won't sift, hasn't eaten for almost 3 weeks

[gummyworms]

Hello,

I got a diamond goby about 3 weeks ago, and am getting very worried about him.

When he first went in the tank, he sifted for about a day, and then retreated to a rock for about 2 weeks. Finally, last week, he came out and now just sits on top of the sand with his mouth open wide, breathing very quickly (~90 breaths per minute). He won't even touch the sand.

He is now looking very skinny and malnourished, and I've tried target feeding him with Prime Reef frozen, frozen brine shrimp, and every kind of sinking pellet I've been able to get my hands on. No luck though.

My sand is quite fine, and I saw the goby sifting the first few days so I don't think particle size is the issue. I have some pictures I will post later, but I wonder if the Goby has some kind of disease? He is getting thinner and thinner by the day and I don't know what to do!

Thanks,
Shawn