Let us get some of the mythinformation out of the way first. A Quarantine (QT) is used to medicate animals. Any and all animals taken from the wild or not properly quarantined previously should be expected to have some sort of disease/parasite. Those who do not medicate risk losing their fish to a various assortment of ailments and several commoners that can kill in less than 24hrs. Most people believe that if their fish is "healthy" and has a sufficient slime coat (inaccurate) that they will not get a disease and their bodies could fight one off to begin with. This is incorrect. Parasites feed from healthy tissue and will leave the host before death follows in hopes of a new victim so you can understand why healthy fish does not mean immunity...it just means a healthy fish will be able to stave off the disease for a longer period, but it will not be rid of it completely.
Now, as for a QT all you'll need is the tank (at least 20g), a heater, a sponge filter, and decor such as pvc
, fake plants, etc. I personally see greater benefits from having the back and sides painted black and the bottom a dark blue so you can see uneaten food on the bottom while keeping the tank dark. The dimness will keep fish more calm while not allowing medications to break down as easily as a directly lit aquarium. As for cycling, it is not necessary because you should be performing 50% water changes daily and most medications will interfere with the bacteria anyways.
A standard QT will last at least 30 days so you can medicate without combination interference. For example, you wouldn't want formalin/malachite green to overlap with a copper dosage. As for actually medicating, Hyposalinity is commonly used to eradicate Cryptocaryon irritans (Marine Ich), but it does not affect Amyloodinium ocellatum (Marine velvet), Brooklynella, etc. Also, Hyposalinity has been reported to cause kidney damage if used long term.
I will make a brief mention of Chloroquine as being considered one of the best medications since it can be used on a variety of sensitive fish and kills Amyloodinium, Cryptocaryon, and Turbellarians; however, it is expensive.
Most popular meds. are Copper (sulfate or Cupramine), Formalin/Malachite Green, Praziquantel, Fenbendazole (Panacur), and Nitrofurazone.