I've used frozen food in metro soaked in focus in my reef very successfully. Just spot feed directly to your fish to keep it from going everywhere. Works.
Internal parasites or internal worms. General cure treats both, Metro only treats parasites, so use GC
I'm treating a TSB for the same thing right now
Mix General Cure with Seachem focus and frozen mysis, feed for 14 days. They eat mostly algae so I also made a paste of GC, Focus and hydrated algae pellets. I mostly dried out the paste with a fan and then froze it. I cut a slice of medicated frozen algea paste every day and drop it, and he gets medicated by both medicated mysis and medicated algae paste. He is better now with 5 days of meds to go
If he's not eating now, the outcome is not good, you must start right away