Dr. Katie and the Fish Tank

Last year, a client kindly gifted My Zoo Animal Hospital with the large fish tank in our lobby.   If you came in at any point while it was getting started, you probably noticed the fish tank was a hot mess.   When I (Dr. Katie) came back from maternity leave in December, I noticed the tank was still a mess, but the team was in the process of cycling the tank again.    When cycling the tank was unsuccessful, the people managing the tank were ready to give up and call it cursed.  I like a challenge so I asked Dr. Debbie if I could take over caring for the tank, and she happily agreed.


I’ve only ever kept betta fish, but I absolutely love my bettas.   I had one 2 years ago, that I trained to swim through a hoop after 3 months of careful and meticulous training, but that’s a story for another day.   Upon commandeering the 44 gallon tank, I carefully examined the tank and created what I thought of as a medical care plan for rehabilitation of our fish tank.  Surely diagnosing and treating our tank’s problem couldn’t be much different from a diagnosing and treating my other patients, right?


My first step was to thoroughly clean the tank and all associated pieces.  All animals have to have the proper environment for good health.   So with the help of a visiting veterinary student (thanks Evan!), we carried the tank outside, hosed and scrubbed the sides, and rinsed every bit of gravel and tank decoration.  Then we refilled the tank and started the filter.   I ordered a few thermometers to check the temperature of the water.  The water was running around 68°F with 1 heater which is too cold for tropical fish to survive.  I ordered another heater and installed it.  After about 1 week, the water was a perfect, cozy 78°F.   All 3 of the tank thermometers were fairly uniform in temperature so I felt confident we had achieved a stable temperature.  The next thing I was worried about was the filtration system.  So Dr. Debbie went to a local pet store and purchased an awesome new power filter with all the bells and whistles able to filter a 75 gallon tank.   I thought it would be more than adequate for our 44 gallon tank.   After my new filter was installed, I let the tank sit for another week then added a bubbler for oxygenation after consulting with my best friend (who is a specialty veterinarian who helps manage a large colony of research zebrafish, thank you Dr. Beth).  I also had the water tested every week.


The Nitrogen Cycle

The Nitrogen Cycle

Once the tank was stable for a few weeks, I was ready to add a few fish.   We added a few platys.  After you add fish to a tank, the tank has to “cycle.”  In short, the fish poop which raises the ammonia levels which is toxic to fish.  After the ammonia levels rise, bacteria that fix the ammonia into nitrites have grow.  Nitrites are still toxic to fish so then more bacteria that can fix nitrites into nitrates have to grow and begin working as well.  Nitrates are less toxic than ammonia or nitrites, but are still toxic in high doses.   Frequent water changes help keep all toxin levels down.  This whole process takes a couple of weeks and generally causes a bit of cloudiness in the tank. Many fish stores will test the chemical levels so you can know when the tank is through with the ammonia cycle.  Once our tank was through, I carefully added a few fish every week or two until we have the population where I want it.  Our last additions were 2 plecostomus to help with our algae.    I have since learned that you can purchase a liquid with starter bacteria to help your tank cycle faster without starter fish, and if I ever start a tank again…I will do that!  Now I have trained all of my teammates to feed the fish only what they eat in a few minutes twice a day, and I do partial water changes every week.  My fish look happy and healthy, and my water is crystal clear.  I’ve enjoyed this project so much; I sort of want a large tank for home so I can actually have time to watch the fish swim.   If you see me out in the lobby of My Zoo, don’t be surprised that I’m tinkering with “my” tank or simply staring at the fish for a few minutes.


Dr. Katie’s favorite fish


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