The process of quarantine is critical to the long-term health and success of your aquarium.  Building a quarantine tank is the easy part but successfully performing the quarantine procedure is what will ultimately result in a long-lasting aquarium pet. 

How Many Fish Can I Quarantine Together?

Ultimately this is dictated by the size of the tank and the size and/or species of the fish. You also have to factor in the available environment for that fish to hide/dwell and feel comfortable.  A 50 gallon QT with nowhere for the fish to hide isn't going to do any good. Fish need available structure and cover to feel comfortable. 

For example, A 20 gallon QT is pretty common.  Add a handful of PVC tubes, maybe some taller plastic plants, and a single rock to the tank. You should have no problem holding 5 community or semi-aggressive reef fish (under 5") with each other. Each fish will have space to hide and this should minimize any territorial aggression. You would run into trouble if you added even a single aggressive fish to that mix and you would also have problems if you tried to add 10 fish of different species to that tank.  

No matter what size the tank might be, you must be able to control the resulting ammonia levels in the aquarium via water changes, filtration, and ammonia detoxifying additives.  The more fish you have, the more ammonia you're going to get, and ultimately the more effort will be required to control that ammonia.

Step #1 - Setup Your QT Tank

The most obvious step, everyone needs a separate QT tank to properly quarantine fish at home so before you buy, build a QT. While you can source fish that are pre-quarantined at the retailer, this can be hard to come by and most often will cost more. Even still, it's a good idea to at least isolate those fish at home and observe for up to 30 days before introducing them to your display aquarium.

Learn How To Build A Quarantine Tank! 

Step #2 - Drip Acclimate

Drip acclimation is the most successful method of introducing brand new fish into an aquarium, including your QT tank.  

Learn How To Drip Acclimate!

Step #3 - Actively Observe The Fish

Once you have the fish acclimated and added to the QT, daily observation is critical. Before medicating anything, you first need to know #1 - if they are sick and #2 - what they are inflicted by. Take 5-10 minutes at least twice per day to look at the fish for signs of illness for at least 21-28 days.

Should a fish perish during this time, you need to restart the observation clock from day 1. This 28-day timeframe is how long it will take a majority of illnesses to show symptoms or various pathogens to run through their lifecycle.  If nothing happens after 28 days, you can be fairly confident the fish are not actively infected with anything.  

Learn How To Look For Signs Of Illness

Step #4 - Water Test & Water Change

Fish excrete ammonia via their waste. Ammonia is toxic to fish and will damage their gill tissue, causing them to suffocate. This is exactly why monitoring ammonia levels in the QT tank daily is critical.

The Seachem Ammonia Alert is a handy device that will visually indicate when toxic ammonia is present at all times but any hobby-grade ammonia test kit will do for daily testing. When ammonia levels rise to detectable levels above 0.2ppm, perform a 50% water change to remove half of the ammonia and dilute what is remaining in the tank.

How to handle pH, ammonia, & water changes in your QT

The pH of your aquarium water affects the toxicity of ammonia, this is how it works. There are two forms of ammonia that can exist and the molecules in the aquarium will change based on the pH. Note: both forms of ammonia show up in your test results, regardless of the form. 

  • Ammonia NH3: Toxic and exists at higher concentrations when pH is above 8.0
  • Ammonium NH4+: Non-toxic and exists at higher concentrations when pH is below 8.0

In your QT tank, pH will drop as ammonia levels build up over time. The low pH of the water encourages a majority of the ammonia molecules to convert into unharmful ammonium. When you do a water change, this will most often cause an increase in pH, immediately converting that unharmful ammonium to toxic ammonia.

The way we combat this immediate toxicity during water changes is the use of ammonia-binding additives like Seachem Prime. Ammonia detoxifiers like this are available from a variety of aquarium companies and should be readily available at your local fish store. Simply use the additives in your QT just before performing the water change.

Step #5 - Treat With Meds As Needed

This is the hardest part of the process because properly identifying and medicating fish is difficult. It just takes experience in order to properly ID illnesses and medicate fish. As a beginner, this is going to be tough should you notice signs of illness. Even if you are not able to properly medicate, just understand you saved yourself from introducing that illness into your display and possibly infecting other fish. QT still has a purpose, even if you are not able to medicate and treat the fish successfully.

If you are lucky, the ailment will be easy to identify or won't show up at all. Should you wish to attempt a medication cycle, do as much research as you can. Follow manufacturer's instructions combined with advice from experts. It is going to take time, 60-90 days or more to fully clear most illnesses so be patient and ideally, your hard work is rewarded. 

Learn More About Identifying and Medicating Sick Fish

Step #6 - Wait 21-28 Days

As mentioned above, fingers crossed that no signs of illness show up for 28 days. It is necessary to wait this entire time because it can take some time for symptoms to show.  So be patient, observe daily, and hopefully, nothing shows up during that isolation period. Remember, if a fish dies or starts to show signs of illness, the clock starts over. 

Step #7 - Move To Display

Only after the fish have been isolated in your QT tank for 21-28 days should you move them into your display. You will need to drip acclimate the fish once again upon transfer into your display.  Also, do not add more than just a few fish at a time into your display.  You may need to move the fish in batches and it is best to wait at least 2 weeks in between new additions into your display.  This gives the biofilter time to accommodate the additional waste levels from new fish. 

Step #8 Sterilize And Store QT Tank Equipment

After you have transferred all of your fish out of QT, you can empty the system and store it away for future use. It is best to empty, sterilize, and completely dry the equipment in between batches of fish.  This way you're not harboring/transfering diseases in the QT.  

How to sterilize a QT tank:

  1. Clean tank walls free of algae
  2. Empty tank
  3. Fill the tank with tap water, add some bleach
  4. Add all of the equipment and supplies to the tank for soaking in bleach water (nets, cups, siphon, filter sponge, filters, pumps, etc.)
  5. Soak for a few hours
  6. Drain, rinse with pure tap water
  7. Let equipment completely air dry 100% and store it for future use