Aquaponics — 13 March 2013

For those of you who have been following along with my aquaponics project, you know that I’ve built an ebb and flow system with a 55 gal barrel, a 32 gal trash can, and a 54 gallon plastic storage tote.  You can see an illustration of it here.  I introduced some gold fish and have had the pump running continuously since Feb 23rd.

The whole idea behind the aquaponics system is dependent on the Nitrogen cycle.  The ammonia from the fish waste is converted to Nitrite and from Nitrite to Nitrate.  The plants in the growbed use the Nitrate, and essentially clean the water for the fish.  So I thought it was time to test the water and see if any bacteria were actually growing.

I read two great articles on Sylvia Bernstein’s website that were a great help to me in understanding how to get the nitrifying bacteria population established for the aquaponics system.  The first article is fishless cycling, and gives recommendations when starting your system without any fish.  The benefit to this method is that you can have extreme swings in pH and nitrogen without worrying about killing fish.  The second article is Starting Up (Cycling) an Aquaponics System Using Fish.  This gives some recommendations to avoid killing all your lovely fish before your even get your system up and working properly.

I have 10 goldfish in my fish tank.  These are meant to be more “sacrificial” fish, since I would really like to get some actual fish I can eat in the future.  To be honest, I’m surprised that they are still alive.

In order to test the water quality, I purchased  the API Freshwater Master Test Kit and a submersible aquarium thermometer.


I got the API Freshwater Master Test Kit in the mail and did my first sample of the water.  The test kit allows for measuring pH, Ammonia, Nitrite, and Nitrate.  Results are found by adding reagents to the water and comparing the color change to a provided color chart.  Here is a picture of the results.

Testing the Water Quality

Testing the Water Quality

I had the following results:

pH = 8.2, Ammonia = 0.25 ppm, Nitrite = 5.0 ppm, and Nitrate = 160 ppm.  The water temperature was 61 F.

Here is the recommended maximum ammonia levels for fish:

Max Ammonia (ppm) for pH and Temperature
pH20C (68F)25C (77F)

I was surprised to see such high levels of Nitrate.  This is a sign to me that the bacteria are being successful and converting the ammonia.  I planted some seeds to introduce to the grow bed.  I’ve also transplanted some broccli and lettuse plants that I hope will lower the Nitrogen levels.  I may need to add fresh water to help reduce the stress on the fish.  Hang in there fish!



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(2) Readers Comments

  1. Wow. A great start on the nitrogen cycle so soon. I’m curious, can you plant seeds directly into the growing medium or do you have to use transplants?

    • I think you may be able to plant right in the growbed, but I’m not sure. I was afraid that the seeds would be washed away, or wouldn’t get enough moisture to start growing. I opted to just do transplants.

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