Just on a remote chance - have you been able to look inside his mouth for any signs of growth, from thyroid, or cancerous growths/tumours? I've seen this a few times over the years, if thyroid related it can typically be cleared up when supplemented with iodine.
www.monsterfishkeepers.com
It just seems like this is something more than just a HITH issue.
Tumor in mouth of giant goby
Any advice is appreciated. My Giant goby stopped eating last week, I thought it odd but my bichirs occasional fast. Today when I was looking at him I saw that he has a giant fleshy Tumour in his mouth. See pics below. I am at a loss, he is a magnificent fish and I hate to lose him, nor...
It just seems like this is something more than just a HITH issue.