Starting your Aquaponics System Using Fishless Cycling

Guest Post by Sylvia Bernstein from The Aquaponic Source

Starting up your aquaponics system (cycling) is a straightforward process if you know what to look for and have a procedure to follow. In a nutshell, you add ammonia to your aquaponic environment, and over time naturally occurring nitrifying bacteria “find” your system, establish themselves, and proceed to convert the toxic ammonia first to nitrites and then to harmless nitrates.
Fish are the obvious source of ammonia since their waste is the eventual fuel that feeds any aquaponics system. Fish excrete ammonia through their gills during their respiratory process, which if left unchecked, will increase in concentration and will eventually poison the fish.

The alternative is called fishless cycling, i.e. getting ammonia into your system by some means other than from fish. This technique has a few major advantages. First, there is much less stress involved (for you and the fish) because you are not trying to keep anybody alive during the process. Because of this, you need be much less concerned about pH since the pH must only be kept in a range that facilitates cycling without consideration for the safety of the fish.

Second, because you can elevate the ammonia concentration to a much higher level than would be safe for fish, you can cycle your system in much less time (generally 10 days to 3 weeks versus 4 to 6 weeks when you cycle with fish) and end up with a more robust bacteria base once you are cycled. The practical result of this is that you can fully stock your tank once cycling is complete, versus gradually increasing the stocking levels as is recommended when cycling with fish. This is especially beneficial to those who are growing aggressive or carnivorous fish because they are less likely to attack each other if everyone is introduced to the tank at the same time.

Finally, you can more precisely control how much ammonia is added to your system during the process. For example, if you see that your ammonia level is creeping up to 10 ppm, but no nitrites have shown up yet, just stop adding ammonia for a few days and let the bacteria catch up. You can’t do this with fish!

There are several ways to add ammonia to your system, ranging from the obvious to the slightly bizarre. I will talk about the pros and cons of each, and you can decide for yourself which makes the most sense to you.

Liquid Ammonia
(AKA Clear Ammonia, Pure Ammonia, 100% Ammonia, or Pure Ammonium Hydroxide)

This is the old fashioned cleaning product your grandmother used to use that filled the room with the smell of ammonia. Only use it if you can find the pure form that is made strictly out of ammonia (usually 5 – 10% by weight) and water. Avoid anything with perfumes, colorants, soaps, surfactants or any other additives. Shake the bottle. If it foams or if it doesn’t list the ingredients or say “Clear Ammonia”, “Pure Ammonia”, “100% Ammonia”, or “Pure Ammonium Hydroxide”, leave it on the shelf.

The hardest part of cycling with pure ammonia can sometimes be finding the ammonia. Where I live, I can buy it at our locally owned McGuckins Hardware. Try your local hardware store, cleaning supply store or even well stocked super stores. If all else fails, you can order it online.

Pros – It is relatively inexpensive (approximately $20 for a gallon) and what you don’t use to cycle your aquaponics system can be used to clean your windows! Plus, you know exactly what you are adding to your system with this product – ammonia and water, nothing more, nothing less.

Cons – Can be hard to find if you don’t have a cleaning supply or a good hardware store nearby. I’m told that it is entirely unavailable in Australia since September 11th because of the remote association as a possible ingredient in bomb making.

Ammonium Chloride (crystallized ammonia)
This is the same concept as the Liquid Ammonia above, but you can find this through aquarium supply stores, soap supply stores, photography supply stores and chemical houses.

Pros – Because it is very concentrated and in dry form, it is inexpensive to ship. If you get the kind intended for aquariums, there will be little doubt that it is pure and will work in cycling.

Cons – There will be cost involved.

Human Urine
(AKA “Humonia” or “PeePonics”)

Sound gross? Well, when you think about it, human urine is actually an excellent source of ammonia just as the waste product from any animal would be. Human urine is just easier to capture. Here is the catch. In order to go from urea to ammonia, you should put it into a sealed bottle for a few weeks to “percolate”. Can you just urinate straight into the fish tank? Sure, but the problem is that since that urine will take a while to convert into ammonia you will have no way of telling just how much potential ammonia you have in there. The levels will read very low, and then all of a sudden one day they will explode. A final concern around “humonia” is that there may be bacteria or germs in your digestive system that could be harmful to the fish and / or the nitrifying bacteria. In general, the conversion to ammonia in that sealed container will destroy most of this. However, the “humonia” approach creates a more complex biological environment than pure, synthetic forms of ammonia and thus introduces some risk to the cycling process and the health of your system.

Pros – This is a free and readily available source of ammonia.

Cons –There is the “yuck” factor, the fact that you have to store the urine until it converts to ammonia, and the possibility that harmful bacteria or germs from your digestive system are transmitted to your aquaponics system.

Other sources of ammonia
As animal flesh decays it lets off ammonia. I saw a suggestion on a forum once for cycling your system using a bit of dead fish, but dismissed this concept as too bizarre. Then I was testing one of my fully established, rock solid tilapia systems with a group of people who had just taken a class from me and were learning about maintaining their system. Imagine my embarrassment when the ammonia reading was off the chart! Ends up a fish had died in the back corner of the tank and hadn’t floated to the surface.

Pros – This is another free and readily available source of ammonia.

Cons – Again, because other bacteria and chemical compounds are given off during the decay process there is a chance that you will introduce something undesirable to your aquaponics system, not to mention the chance of attracting flies or other insects that want to assist in the decomposition. The other issue is that it will be very difficult to control how much ammonia gets into your system with this method.

Instructions for Fishless Cycling
Once you have identified your source of ammonia you are ready to start the cycling process. Just follow these simple instructions.

Add the ammonia to the tank a little at a time until you obtain a reading from your ammonia kit of ~5 ppm.
Record the amount of ammonia that this took, and then add that amount daily until the nitrite appears (0.5 ppm)
Once nitrites appear, cut back the daily dose of ammonia to half the original volume.
Once nitrates appear (5 – 10 ppm), and the nitrites have dropped to zero, you can add your fish.
Couldn’t be much simpler, or more stress-free.


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