Thanks for the feedback.
Unfortunately my local fish store told me he'd be fine in my tank with the fish I have when I bought the shark egg.
I do think I know what's wrong now. It's an internal parasite. Maybe a tapeworm. I thought my bird wrasse had died so moved rock to get him out. He hadn't moved in days. He surprisingly was still alive but looked like he was being eaten from the inside out. I took him out and put him in QT with prazipro. A white worm has slowly started working its way out of his intestinal tract. My bird wrasse is still alive. Poor guy :-(
It can't be coincidence that my two bottom dwellers are acting ill. I think it's safe to assume that my shark may have the same parasite inside. I've added prazipro to the tank my shark is in, increased aeration, turned off skimmer and removed carbon. My shark is still eating so praying he pulls through this. I wish I would have dosed my tank days ago but hate jumping into medicating fish until I go through process of elimination.
My plans are to get a 500-1000 gallon aquarium in the next year or so and will move my shark to that tank if he pulls through this. Breaks my heart as I'm so attached to him. I also rearranged my rock to give him more swimming space. He likes to swim through the PVC pipes so I added another long one to give him more hiding places.