Tank Dwellers

Teaching The Basics Of Aquariums To All

How To Properly Cycle An Aquarium

Aquarium Basics / by

Cycling an aquarium is the most important thing you will do before purchasing fish for your new tank. It allows you to add fish with the confidence that any waste produced is quickly converted from the harmful ammonia to the safer, nitrate. The unfortunate part about cycling is that many stores either misrepresent how the process is carried out or fail to even inform people who are new to the hobby how essential this step is.

Cycling – Purpose

The purpose of cycling a new fish tank is to prepare your aquarium to carry out the nitrogen cycle. This is the incredibly important process which converts harmful ammonia created by fish and food first into nitrite, then the relatively safe nitrate. This is essential because the ammonia (as well as the nitrite) are very poisonous to the fish who excrete them and even in low concentrations can be fatal. Instead of allowing this to happen our goal as aquarists is to build up the beneficial bacteria which carry out this process so our fish are never harmed.

Something you commonly hear in big chain pet stores (although certainly not every one of them) is to “set the tank up and let it sit for a day or two, to cycle it.” Although I love that cycling is even mentioned, this is simply not enough to accomplish anything. The process of cycling a brand new fish tank is more elaborate than this statement makes it appear. So below I will lay out the various methods and explain the benefits and risks related to each method. For all of these methods you will first need an aquarium which has been fully set up.

Fishless Cycling

Fishless cycling is exactly what it sounds like. It involves setting up your tank before any fish are introduced. If you cycle your aquarium without fish you eliminate the risk of killing any during the early days of the tank and as such you will save money. The downside is that the bacteria you are trying to grow won’t colonize overnight, so if you have a child who wants fish now they may be a little disappointed. I personally see a little disappointment in having to wait significantly better than seeing the sadness a dead fish can bring, which is why this is the method I always use.

Steps – For The Beginner

  1. OPTIONAL: Speed up the process by creating the ideal environment for bacteria to grow by adjusting your heater anywhere between 77 F and 86 F (25 – 30 C). Additionally turn your air pump to full and let your airstone do extra work.
  2. Begin ghost feeding your fish tank, this entails adding fish food to your tank the same way you would if the tank was fully stocked. This introduces ammonia which is the food source for the bacteria you are trying to grow.
  3. Measure the level of ammonia, nitrite, and nitrate every couple of days and recording each of the levels in a notebook.
  4. Eventually you will begin to notice the level of ammonia and nitrite BOTH dropping while the nitrate continues to rise.

If you perform this type of fishless cycle, it could take as long as 4 to 6 weeks to cycle your aquarium. This is by no means a perfect way to cycle your tank, but you can add a small number of fish without having to worry about the ammonia they produce. By no means would I fully stock the tank even after a successful cycle, but if you continue to add more fish every week or two, you will end up with a fully stocked, lively aquarium.

Steps – Intermediate Version

  1. Purchase a source of pure ammonia from your local hardware store and an API Master Test Kit from your local fish store.
  2. OPTIONAL: Speed up the process by creating the ideal environment for bacteria to grow by adjusting your heater anywhere between 77 F and 86 F (25 – 30 C). Additionally turn your air pump to full and let your airstone do extra work.
  3. Now add your ammonia until the concentration hits 4 ppm. Depending on the ammonia you purchased the amount to add will vary. The best practise is to add a small amount, then test your tank 20 minutes later to measure the current concentration. A good starting place is 2 to 4 drops of ammonia per 5 gallons of water.
  4. Begin testing your ammonia level every couple days. Eventually as the bacteria begin to colonize, the ammonia will drop. Do not allow the ammonia to get lower than 1 ppm or you will begin to starve the bacteria.
  5. With ammonia dropping, it is time to begin testing nitrite. This will not go up immediately after you begin losing ammonia, but with time it will.
  6. When your nitrites begin to get high, begin testing for nitrates (still testing once every couple of days). Eventually both nitrite and nitrate levels will be high enough that they go off the testing scale, at this point do a 50% water change.
  7. As time progresses, you will find a day when you add ammonia and the next day all of it (including the nitrite) will be gone. At this point it is time to double check that you have fully cycled your tank. Get your aquariums ammonia concentration to 4 ppm again, and if after 24 hours all of the ammonia and nitrite are removed once again you have successfully cycled your tank.
  8. At this point, you want to keep your bacteria alive. Continue to add 1 ppm of ammonia to your tank each day until you add fish to your tank. The night before you add fish, make sure to lower the temperature to a level they can tolerate. On top of this, perform a 90% water change once more to get the nitrate levels to a safe level for your fish.

If you perform this type of fishless cycle, it could take as little as 20 days to cycle your aquarium. On top of that you technically could add enough fish to fully stock your tank because you have created a colony of bacteria that can process extremely large quantities of ammonia before it has a chance to do harm. Despite cycling my tanks using this method, I still never add a large quantity of fish just to make sure the fish tank can handle them.

Fish-In Cycling

As has been said previously, fish-in cycling has inherent risks. If you add too many fish at once and forget to monitor the water chemistry it is very likely you will lose fish. Some consider this method harsh and the fish you use to cycle the fish tank are commonly referred to as “sacrificial.” Others see it as the only way to cycle an aquarium as they can not stand waiting the 20 days to 6 weeks to guarantee no fish will be harmed. Whether or not this method is preferred the fact is a lot of people go to a pet store, pick up a new aquarium, and buy fish the same day and this is simply their only option.

Before you begin a fish-in cycle realize any fish you add to your aquarium are at risk of ammonia spikes and may be harmed. Because of this, it is imperative to plan beforehand. Your goal when doing this type of cycle is to very lightly stock your tank. This means, if you have a 10 gallon tank, you should get a fish that is less than an inch long (as a general rule) in order to limit any risk of harming them. In addition to this, realize this fish (if everything is done correctly) will survive so make sure to pick a fish that you both like AND is known to be hardy.

Steps

  1. Add fish in the quantity you have decided which are also known to be relatively hardy.
  2. Test the water parameters at least once every other day in order to catch any spikes in ammonia or nitrite. If one does occur, a water change of approximately 50% should be performed in order to keep levels safe.
  3. While continuing to check the water parameters, perform weekly water changes of 50% (twice a week would not hurt) in order to keep levels of harmful molecules low.
  4. Continue this process for approximately 1 month, after which you can begin to add additional fish (again in small quantities) every other week until fully stocked.

Plant Cycling

Plant cycling is a newer method to me but may be my new favorite way to cycle an aquarium. The premise is quite simple, you set up a fish tank, add a large number of plants to the aquarium, and after a short time fish can be added. The benefits of plant cycling are that you add living material to the aquarium which immediately gives that full appearance, and you can add fish relatively quickly. You also know that if any ammonia or nitrite spikes occur the plants will assist in processing these which makes the spikes much more mild. The best plants for this method are those that grow quickly but won’t shadow the others. These include: hygrophila, guppy grass, hornwort, water sprite, java fern, and cryptocoryne.

  1. Acquire a light which will be able to grow the plants you desire and stock your tank heavily with these plants (variety is important).
  2. Add a light stocking of fish. An example of this is if you have a 10 gallon tank you would only add fish with a total length of one inch.
  3. Create a schedule in which you test the water parameters approximately every other day to test for spikes in ammonia or nitrite (doing a 50% water change if one is seen) and performing 50% water changes every week.
  4. Continue this process for roughly 3 weeks at which point if you see no more toxin spikes you can begin adding more fish every week to 2 weeks.

The reason I like this method the most is it provides a nice buffer to toxins while allowing you to relatively safely add fish to your aquarium. One of the biggest complaints I hear when I describe the process of cycling is that people (and their children) hate sitting with an empty cube of water. For this reason a plant cycle really deals with the problem of making the aquarium safe and keeping interest.

Seeding Bacteria

With every single method listed, one of the simplest ways to speed up your cycle is to get material from an established tank and add it to yours. The beneficial bacteria that are desired in your aquarium will grow on your substrate, plants, decorations, in the water column, but most of all within the filter itself. If you can take anything from an already cycled aquarium you will be adding an already successful colony of bacteria directly into your tank to help kick start their growth and speed up cycle times. Something as simple as squeezing a used filter into a new aquarium can really cut down on the time you wait for a successful cycle.

With this being said, many products exist that claim to contain all the bacteria you need to cycle your aquarium. I personally have always looked at these products with skepticism but do believe they can introduce some extra bacteria to your tank. I would never do the prescribed three day dose of these products then fully stock my tank, but I may use one and begin a fish-in cycle with less worry than normal.

Whatever method you choose to cycle your tank, the important part is that this process is completed thoroughly. Without a cycled tank you risk a spike in toxic ammonia and nitrite which can be lethal to your fish and costly. Guaranteeing your bacteria are in sufficient quantity that they can handle these chemicals allows you to sleep more comfortably and know with certainty that adding more fish will not cause a sudden crash.