How to Cycle Aquaponics System Without Fish?

Last Updated on December 14, 2018

Cycling your aquaponics system is a simple process if you know your aim and procedure. It just takes adding ammonia to your aquaponic environment. Over the time, naturally occurring nitrifying bacteria will colonize in your system and will start converting the toxic ammonia first to nitrites and then to harmless nitrates.

Nitrogen Cycle: Ammonia > Nitrite > Nitrate
Nitrogen Cycle: Ammonia > Nitrite > Nitrate

Many of you might think that fish are the key to making aquaponics work, but you would be wrong.

The real key in aquaponics is ammonia because there is no nitrogen cycle without the ammonia.

What about the fish? Well as the fish go about their day, they produce a fair amount of ammonia. They breathe through their gills, pee, and poop, all creating ammonia.

Now, We know that in order to begin the nitrogen cycle we need ammonia. This is where the fish come in! Well, that would be one way to go. It is a method called fish cycling.

Also, read How to Cycle Your New Aquaponics System with Fish

You don’t want to lose your fish for the aquaponics system after carefully looking at all factor to choose the fish for aquaponics. So you may not want to put your fish in the tank before it is cycled or cycle the tank with fish.

In order to avoid fish loss, an alternative method to fish cycling is fishless cycling.

Ways of Fishless Cycling

We’ll talk in this article about cycling the system without fish. I recommend cycling your system without fish if you can wait but for many, it’s too late and the fish have arrived or you just can’t contain yourself.  There are many great benefits to cycling without fish like:

  • It is faster. The fishless method takes between 10 days to 3 weeks as compared to 4-5 weeks in the case of cycling with Fish. This is because you can elevate the ammonia concentration to a higher level than would be safe for fish.
  • You do not have to worry about any loss of your fish. So nitrite and ammonia spike which is normal during the process will not bother you. Also, You can keep the pH in a range that facilitates cycling without consideration for the safety of the fish.

You can also grow plants during the cycling and you don’t lose any fish. It gives you more of an understanding of how to manage the system and is probably less stressful for you and the fish.

Also, if you have a kickstart like a pond capsule bacteria or a safe and clean fish tank that is already cycled it goes faster.

If all goes well it can happen in as little as 3 weeks, but you should probably plan on 6 weeks.

You should test the nitrates, nitrites and make sure the pH is bacteria friendly too, that is a more accurate way to test.

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

1. Liquid Ammonia

(AKA Pure Ammonium Hydroxide)

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.

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.

2. Ammonium Chloride (crystallized ammonia)

Simply add chemical ammonia to the aquarium water and let the process cycle. You can somewhat accurately determine the amount of ammonia being added to the tank.
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To speed up the cycling, You can add live nitrifying bacteria (along with ammonium chloride). This will cycle the tank in less than one week. Again, do not add too much ammonia. Just adding 1-4 drops of solution to 1 gallon of aquarium water will result in an ammonia-nitrogen concentration of 2 mg/L (ppm).
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The procedure is to add the ammonium chloride solution, shake the bottle of nitrifying bacteria well and add it to the aquarium. Measure ammonia and nitrite the next day and record. Add ½ dose and wait 24 hours and measure again. By day 5 to 7, you should be able to add 4 drops per gallon and the next day, ammonia and nitrite will be 0.

Why do you need proper ammonia?

Most of the ammonia solutions that are easy to find are for household cleaning use. They usually contain an additive for scent or something else. Also, many of the ammonia cleaning solutions which have a heavy ammonia order also have very high pH and the smell is ammonia gas.

Over time, the ammonia is leaving the solution, so the concentration is changing (getting lower). Most start out between 4 and 11% ammonia but rarely is the concentration given on the bottle, so it can be hard to figure out how much to add.

If you are going to use an ammonia solution, proceed cautiously at first until you have an idea of how much ammonia is actually being put into the aquarium water. For this, you need to be able to accurately measure the amount of the liquid you are putting into the water. Add some solution to your aquarium, let it mix and then use your test kit to measure the ammonia concentration in the water. You want to have an initial ammonia-nitrogen concentration of 2 to 3 mg/L (ppm). Do not go above 5 mg/L.

3. Human Urine

Otherwise known as 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 an animal would be.  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.

Urine is composed of urea. 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.

Also, 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.

Pros – This is a free and easily 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.

4. Dead Shrimp or Fish

One of the more popular fishless cycling methods is to use a bit of dead fish or shrimp. As animal flesh decays it lets off ammonia.

Get a few dead shrimp or fish at the grocery store, cut them up into chunks and add them to the tank.

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

Cons – You will really have no way to know how much ammonia is being produced by the decaying shrimp, and the aquarium does not look very good with dead shrimp laying on the bottom. Also, the organic material of the shrimp can cause bacteria blooms which turn the aquarium water cloudy. 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.

A must-have for an Aquaponics System:

Other sources of ammonia

Note that some people use flake fish food. This is not a good way because flake food does not have much organic material compared to shrimp and so does not add a lot of ammonia to the water, but you can use cut fish instead of shrimp.

Instructions for Fishless Cycling

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

  1. Add the any of ammonia source (mentioned above) to the tank a little at a time until you obtain a reading from your ammonia kit of ~5 ppm.
  2. Record the amount of ammonia that this took, and then add that amount daily until the nitrite appears (0.5 ppm)
  3. Once nitrites appear, cut back the daily dose of ammonia to half the original volume.
  4. 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.

Tips and Troubleshooting:

  • Do not let the ammonia or nitrite concentration get above 5 ppm. If either ammonia or nitrite concentration gets above 5 ppm, do water changes to lower the concentration.
  • Do not add ammonia removers to bind the ammonia. The cycling time will increase because of these products.
  • Do not let the pH drop below 7. If it does, do a partial water change to bring the pH back up.
  • You do not have to add ammonia every day – the bacteria do not require feed every day. Adding ammonia every day will results in a sky-high nitrite reading and slow the cycling process.
  • If your tank does not have a substrate (gravel or crushed coral) on the bottom (bare-bottom tank). Then, it will take longer to cycle because there is not very much substrate for the bacteria to adhere to. If you are setting up a quarantine tank and do not want to use a traditional substrate consider adding some inert glass rock or marbles or some other non-calcium-based media to the tank bottom. This will help cycle the tank faster.


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