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Speeding Up Cycling (Starting) an Aquaponic System

March 4, 2010

So now that I have had a chance to “wax eloquent” about how aquaponics is bacteria farming at its core I thought I would write a slightly more practical post about how to attract all that wonderful nitrifying bacteria to your system in the first place.

Just to be sure we are all on the same page, what I’m talking about is the process of establishing your bio-filter (base of nitrifying bacteria to convert ammonia into nitrates) in the media when you first set-up your aquaponics system. The nitrosomonas bacteria that start the process by converting ammonia into nitrites occur naturally and will find your system if ammonia is available to them. This then attracts the nitrospira bacteria that converts the nitrites to nitrates and completes the process. Once in place, this process runs continuously. Getting the process fully engaged takes roughly 4 weeks, during which time your fish will be extremely stressed and your plants will be food-free.

With the help of and bits of knowledge I’ve gathered over the past year I have assembled a list of ways to shorten that cycle time to closer to 2 weeks.

There are two types of cycling in any fish system – cycling with fish (i.e. letting the fish generate the ammonia), and cycling without fish (adding other sources of ammonia). If you decide to cycle with fish you should assume that many of your fish are sacrificing their lives to the greater good of creating the bio-filter for the generations that succeed them. Don’t start your system with prize koi! I would also hold off on tilapia and other hardy food fish at this stage just because you generally buy these fish from hatcheries in larger batches than you can buy pet-store fish, and it is generally not so convenient. Save that drive for when the system is free of ammonia. Rumor has it that Black Skirt Tetras can survive just about anything, and goldfish, zebra danios and barbs also work well. Avoid feeder-goldfish, however, as they are often diseased. You should only feed your fish once a day until the ammonia is gone to avoid ammonia overload.

The less death-defying method is fish-less cycling. I’ve listed some of the ways of doing this that I’ve come across, in order of how I would recommend them.

  • Add media and water from someone else’s fully cycled system or aquarium or borrow the filter pad from an aquarium and let it soak in your aquarium overnight. This is ideal because rather than adding ammonia and waiting for the bacteria to come, you go straight to adding the bacteria. A member of commented “in the aquarium hobby, we call it Precious Holy Goop, squeezed from the filter sponge of a friend’s tank, with prayers and incantations to encourage it’s growth explosion in our tank…” How lovely.
  • Add pond or river water. Again, this is the notion of adding established bacteria directly to your system vs. attracting it with ammonia. More risky than the first solution, however, as you can’t know what else you are inviting into your system through the “wild” water.
  • Add pure ammonia (Clear Ammonia or Pure Ammonia or 100% Ammonia, or Pure Ammonium Hydroxide) and liquid seaweed (Maxicrop). See the two methods below for specific instructions on how to use this. The Maxicrop will add in some additional bacteria, and is great for your plants until you can get your system really cycled. I’ve used it with great success.
  • Vermicompost (Growing Power method) – see my earlier post on Aquaponics, The Growing Power Way.
  • Buy off-the-shelf starter product – I’ve seen mixed reviews on this so I can’t really recommend, or not recommend this at this point.
  • Try humonia or “peeponics”. This is literally peeing into your tank once a day. The guys at Earth Solutions have lately talked about this as a way to grow, even without fish. I can’t get quite get my mind around it, but I have to admit that we tried it once and my husband thought it was great. Guys seem to like that sort of thing.
  • Add bits of raw fish – apparently raw fish releases ammonia as it decomposes, but again I would wonder what else was being introduced along with the ammonia.

For you chemistry buffs, the cichlid forum has two very specific, scientific “recipes” for speeding up nitrification using commercial grade ammonia:

  • 1st method – 4-5 drops of NH3 / 10G / daily until NO2 peak, then reduction to 2-3 drops of NH3 / 10G / daily (this recipe uses ACS grade ammonium hydroxide ~28% NH3)
  • 2nd method – (They claim that this one is used by probably 99% of cichlid hobbyists). Addition of X amount of NH3 drops until Ammonia level of 5ppm is achieved. This X amount of drops has to be added daily until NO2 spike. Afterwards follow up with X (from previous step) amount of NH3 drops daily until NO2 is 0ppm causing NO3 peak.

Other steps you can take to insure that you get through the dangerous waters of cycling as quickly as possible are to keep your water temperature warm (bacteria love warm, wet environments). The mid 80’s F. is best. Also be sure that your water is well aerated and that you keep your pH close to neutral – the higher the pH the more toxic the ammonia becomes.

After 2 – 4 weeks you will see the ammonia levels drop to near zero and beautiful nitrates will start to appear in your chemical tests (you should be testing ammonia, nitrites, nitrates, and pH levels at least once every couple days if for no other reason than to witness the drama of this cycle being played out). Your pH will drop. Your plants will green up and your fish will start to eat. All will be right with the world of aquaponics and you can thank the nitrification gods that you only have to do this once!

3 Comments leave one →
  1. Richard Andrews permalink
    March 5, 2010 7:31 am

    Query: Could you use readily available fish emulsion soaked in a pad, add a bit of ammonia to restart the bacteria? This prep could be done a couple of weeks prior to adding to your system.

    • March 5, 2010 8:26 am

      My understanding is that fish emulsion is ground up fish that has been fermented for use as fertilizer. I can’t imagine how that would jump start the nitrification process, especially if you are already adding a pure source of ammonia…but I’m not a scientist. What I recommend is that you join and ask this question there. I can point you to a couple members that have advanced science degrees, and also happen to be aquaponics enthusiasts, who could do a much better job with this.


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