This thread contains all the information presented at the BAR New Hobbyist workshop on Saturday, April 12, 2014. Feel free to chime in with questions and your experiences. Why do we need to cycle? What does it mean to cycle? All living organisms produce ammonia as a waste product from consuming food. Levels of ammonia can quickly become toxic in our aquariums as animal waste builds up. Even low levels can cause undue stress to animals such as coral or fish. This is why it is so important to cycle your aquarium -- you want to ensure that the animals in your care are provided with a clean, safe environment where they can thrive and give you many years of enjoyment. The diagram above illustrates the nitrogen cycle as it pertains to our aquariums (Wikipedia has a wealth of information on the nitrogen cycle). In the ocean, ammonia produced by animals is converted by various types of bacteria into progressively less harmful nitrogen-based substances. The bacteria that do this are plentiful in the ocean. However, unlike the ocean, our aquariums contain a small volume of water, and often have little to no beneficial bacteria when we set them up. Getting the tank ready Before you cycle your tank, you have to set it up! The other BAR New Hobbyist stations will cover important topics such as RO/DI water, salt mix, salinity, etc. The first step to setting up your new tank and preparing for a cycle is to ensure the tank is set up, filled with clean fresh saltwater, and your heater is running. Before adding any salt water to your tank, test your saltwater for ammonia, nitrite and nitrate. This is a good time to verify that your salt mix is good, and that your reverse osmosis unit is operating correctly. If you opt to use conditioned tap water, there is a chance that the tap water already has ammonia, nitrite or nitrate in it, so its good to know this before starting the cycle. Alright, lets cycle the tank! In order to cycle your tank, you need: A source of ammonia - required to feed the bacteria and help the bacteria population grow. A source of bacteria - required to establish the bacteria population. An ammonia, nitrite and nitrate test kit to measure levels - required to see where in the cycle process you are. Patience. - this will be required for any adventures in marine aquarium keeping. You will notice something absent from this list -- a fish. It is a common misconception that the best way to cycle an aquarium is to set it up with a "hardy starter" fish that will provide the bacteria and ammonia required to get the cycle going. Using a fish to start the cycle, even an inexpensive or "hardy" one is not a good idea. As the levels fluctuate during the cycle, the fish will be stressed and face a high chance of dying, or falling ill to a disease -- neither are great options for a new tank. This discussion assumes you want to cycle the tank WITHOUT using a fish. The next few paragraphs discuss where we can get the ammonia and bacteria to cycle a tank. If you are starting a tank using live rock (rock that has been in another aquarium, is from the ocean, or is aquacultured) or live sand you already have a source of bacteria which can be used to cycle the tank. Alternatively if you start with dead rock (ie dry base rock) and dry sand you can get a scoop of sand from another aquarist's tank. Both of these are great sources for bacteria to help get the cycle started. For a source of ammonia, pure 10% ammonia is an excellent choice. If you got ammonia at the BAR New Aquarist workshop, you can use that. If you need to buy more, get “Janitorial Strength Ammonia” from Ace Hardware. This brand is free of dyes, foaming agents, etc. You know an ammonia source is pure if when you shake the bottle it does not foam. An alternative to using ammonia is to use a FRESH raw shrimp purchased from the grocery store. Putting this in your newly set up tank will provide some bacteria to start the cycle (though a sand sample or live rock are still a good idea), and most importantly as the shrimp rots, a steady source of ammonia. If you decide to cycle your tank using 10% ammonia, the table below shows approximately how much ammonia must be added to your aquarium to achieve 3 ppm (3 ppm refers to the CONCENTRATION of ammonia in the tank) of ammonia, which is sufficient to start a cycle. As a rule of thumb, it is best to wait until ammonia and nitrites have both dropped to zero before adding fish. Wait until nitrates are low or undetectable before adding coral. This also gives the tank time to mature. The following graph illustrates how the ammonia, nitrite and nitrate levels will change over the course of the cycle. It can take upwards of 20-30 days for a tank to fully cycle. Note: The levels and times are not intended to be accurate and are for illustration purposes only. Volume (US Gallons)Ammonia Required (mL) 10.11 50.57 101.14 202.27 303.41 404.54 505.68 606.81 707.95 809.08 9010.22 10011.36 15017.03 20022.71 25028.39 30034.07 35039.75 40045.42 45051.10 I've added ammonia, what now? If you've added ammonia, use your ammonia test kit to check the ammonia level and adjust if needed. If you started with a raw shrimp, you can wait a week before testing the ammonia. It will take some time before the shrimp starts to rot and the appropriate ammonia levels are achieved. You'll notice when you look at your ammonia, nitrite and nitrate test kits that they all tell you the concentration of each in ppm (or mg/mL). These measurements are telling you the concentration of ammonia, nitrite or nitrate in your tank. For those not familiar with chemistry, it is important to note that concentration is not a measurement of how much of something there is in your tank total, but a measurement of how much of something is in a fixed volume of water. If you were to measure ammonia, nitrite and nitrate every day and graph the concentrations of them, you might see a graph similar to this: The important thing to note is that as bacteria establishes to convert ammonia to nitrite, for example, you will start to see the ammonia levels drop, while nitrite levels will increase. Similarly as bacteria establishes to convert nitrite to nitrate, the nitrite levels will drop while the nitrate levels will increase. Finally, when bacteria to convert nitrate into atmospheric nitrogen establishes, the nitrate levels will drop. If you started your cycle by adding ammonia, you'll of course have skipped the first few days of the graph where the ammonia level is increasing slowly. Once you have started the cycle, every second day (or every day if you desire), measure the ammonia in your tank and record it. To start there is no need to measure nitrite and nitrate (because there are none) -- though feel free to measure them if you want to get more familiar with your test kits. Once you start seeing the ammonia drop, its time to start testing nitrite as well. Once you start to see nitrite, every other day you can add a little bit more ammonia to bring back the ammonia level to the level you started at (3ppm). This helps ensure you are actively feeding the bacteria to sustain its population. Once you start to see nitrite dropping, its time to start testing for nitrate. Once nitrite drops to almost zero and your ammonia additions are consumed within approximately 24-48 hours, your cycle is ALMOST done. When nitrite is zero, it is safe to start by adding your first fish. This this point its still important to keep measuring Keep an eye on the levels every other day as the new fish adjusts. In the unlikely event you detect a spike in ammonia, a 50% water change should be performed every day to help get the ammonia levels back down below 0.05ppm. Provided you have sufficient live rock and sand, the nitrates should start to drop. Once they reach near 0 you can begin considering your first coral addition The key throughout this process is to have patience. With each new fish, coral or invertebrate addition you should monitor your levels to ensure the aquarium adjusts its bacterial carrying capacity appropriately. Some important notes: A death of a fish, coral, or other creature can cause a spike in ammonia and a new mini-cycle to start. If you detect ammonia at any point, aim to perform large 50% water changes daily to bring the levels down and protect the tank inhabitants. Over-feeding can also cause a spike in ammonia levels. What can go wrong? If your cycle seems to have stopped progressing, here are some common problems: Not having a sufficient “starter bacteria” load. Try getting some more sand or filter material from an established tank. If any of ammonia, nitrite or nitrate gets too high. If you see a lack of progress, a high reading of one of these could cause the cycle to stall. Perform 50% water changes daily to help bring the levels down (ammonia < 5ppm, nitrite < 10ppm, nitrate < 20ppm) and see if the cycle resumes itself. In any case, feel free to post questions/comments here. Share and help others!