The hobby of successfully keeping fish - meaning, both you and the fish are happy and healthy, requires much patience, constant learning, lots of trial and error and sometimes, just pure dumb luck.
Anyway, here's why I always have a couple, small spare fish tanks handy...
- Quarantine Tank:
New fish can easily introduce a bacteria or virus into your community tank and wipe out its inhabitants.
That's why any newcomers to the community tank should be quarantined for at least a week until observation proves they are not a biological threat to other fish.
- Hospital Tank:
Like any living creature, fish can succumb to illness or the aftereffects of injury - usually, infection or a myriad of physical impairments.
IMHO, sick fish require EARLY INTERVENTION with medications to survive an illness or infection.
EARLY INTERVENTION can prevent the sick fish from going belly up and becoming "Patient Zero" (aka the bacterial or viral source responsible for a lethal, tank-wide pandemic).
About Antibiotic Therapy:
In addition to killing bacteria that cause fish diseases, antibiotics can also eradicate the essential, "Good Bacteria" needed to complete the Nitrogen Cycle within the tank; meaning, your tank crashes and the water chemistry goes haywire (i.e., "red zone" pH, ammonia, nitrite and nitrate levels).
About Methylene Blue Therapy:
Methylene Blue Treatments provide a host of benefits for fish. It effectively prevents and protects against superficial fungal infections of fishes and also protects newly laid fish eggs from fungal or bacterial infections.
As secondary use is treatment against some external protozoans, including Ichthyophthirius (Ich).
BUT...
Methylene Blue stains everything!
Unless you want to have blue fingers and hands for days, always wear gloves when handling Methylene Blue.
Lastly, Methylene Blue kills most snails and shrimp.
My "Quarantine" and "Hospital Tanks"
Submitted FYI.
May you and yours be well and loving life today.
In Lak'ech,
JaiChai