I have never seen this behavior from him. He hangs out at the bottom of the sand in the open all the time but never constantly swims. He did it for about thirty minutes and I tried feeding him and he wasn't interested. Now he disappeared to his cave. Tested for ammonia it was zero. Other fish seem fine. Two clownfish and a tailspot blenny. Tailspot was added a month ago. Purchased it already quarantined. Is he OK?