This is how frozen foods come, they are in little punch through packets (like some types of gum come in). https://www.aco-aquariums.com.au//up...ulinaCubes.jpg
The other side is a thin foil so you can just push the plastic side and it'll pop out the other side.
I use a little jar for mine, I pop one section out into it, and let it thaw out on the counter. Once it's thawed (usually takes no longer then 10 minutes) I grab a "fish only" pair of tweezers and grab a pellet sized amount and drop it in the water. I think that amount would be enough for him for quite awhile since frozen foods can make them a little chunky for awhile. When you're done feeding put the lid back on the jar and place it back in the freezer until the next feeding.
If he has some kind of fungus you can try to medicate him with either Maracyn - which is powder, Maroxy - liquid, API Fungus Cure - powder or you can try and go back to Aquarium Salt with daily water changes 1 tsp per gallon. And any of these can be used along side an Epsom Salt bath. You can be treating him for his fungus and take him out daily for 30 minute ES baths at 1 tsp per gallon which will help with any internal parasites.
If there are external parasites then Maracide is a good one to use. It has easy to follow instructions on it's bottle as well.