I've heard of soaking in garlic and vitamins...not vinegar. I'd think that the acidity would kill (or seriously harm) your fish if they eat it and compromise your water quality...I wouldn't recommend it.
It must have been a filipino aro. He liked shrimp adobo.
Don't be to worried just yet. When I get an aro, I don't even offer food for about 4 days. They can live a long time without food. Let him get used to the tank first.