Unfortunately, most LFS
are in it to make money. They know they can sell most people fish with the aquarium. Then, when they die, they will come back for more remedies and fish. It is an ongoing cycle where you just keep spending money there. Not to say all are like that, but most are. Ask your questions here and we will help you through it. You will need to do daily water changes to keep ammonia from building up and killing your fish. I would not add any medicines right now. Your best defense is good clean water. That alone can fix alot.