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Cycling Primer

PostPosted: Sat Nov 29, 2008 6:58 pm
by Crazygar
A Cycling Primer
By: Kieron Dodds

There are so many levels of enjoyment and involvement in this hobby that it’s impossible for every aquarist to see things from every other aquarist’s point of view, and a tremendous number of “advanced” hobbyists will often frown upon the lack of a beginner’s desire to learn certain things. If you are just starting out in the hobby, you may find yourself confused because aquarists with more experience and knowledge are aghast that you don’t have an intimate knowledge of the cycling process, despite your success. From the opposing point of view, if you are a more experienced hobbyist, you may think that there is no way another hobbyist can be successful without a working knowledge of the cycling process. From a subjective standpoint, either point of view may be correct for an individual hobbyist. It is important to understand that what works for one hobbyist is not guaranteed to work for all. There is a point to all of this, so please bear with me.

Cycling, in terms of preparing an aquarium for fish, refers to the Nitrogen Cycle, a biological process by which Nitrogen compounds are used and reused as waste products or nutrients by different organisms in a continuous circle. Some of the byproducts of this “circle of life” are toxic to fish, which is why we, as aquarists, need to complete the circle in our aquaria before adding its final animal inhabitants. This article will differ from other articles previously written on the subject in two ways. First, it will differ in its insistence that it is not important for you to understand the workings of the cycling process. Second, it will provide alternative methods not often discussed in print. Of course, understanding the process can be helpful, but it is not necessary as long as you know a very few, very simple facts.

The usual introduction to an article on “Cycling” treads, briefly or in-depth, into the workings of the Nitrogen Cycle. Well, for the purposes of maintaining a successful aquarium, we, as a whole, really do not need to know the intimate processes of the Nitrogen Cycle, nor do we even need to know what Nitrogen itself is. There are a few things we do need to know, however, and these are very simply put and easy to remember.

    1. Ammonia and Nitrite are byproducts of the metabolism of the animals (and to some extent plants) we keep. These byproducts are toxic to fish at all levels of concentration measurable by commonly available test kits. Some have asserted that Ammonia and Nitrite are more or less toxic depending on other water parameters. Toxicity, however, is absolute in this instance. Any measurable levels of Ammonia or Nitrite will have toxic effects upon the fish or other animals in the tank. How quickly these effects are realized or how badly they are expressed as symptoms may change, but that does not change the fact that these compounds are harmful. Neither does it change the fact that these compounds can and do compromise long term health, sometimes even after very limited exposure. Nitrate, the final byproduct of the nitrogen cycle in many systems, seems to be non-toxic to fish even at very high levels. However, it does promote nuisance algae and bacteria “blooms” and, as such, should be kept as low as possible.

    2. Due to the above, it should be our goal to maintain existing aquaria that never reach any measurable level of Ammonia or Nitrite once long term inhabitants are going to be added. It should also be our goal to insure that this does not happen in new aquaria.

    3. The process of insuring that Ammonia and Nitrite do not reach harmful levels in new aquaria is called, generally, “cycling”, and you need to do it. You need to measure Ammonia and Nitrite throughout the cycling period to insure that Ammonia and Nitrite have both “spiked” (reached a high point) and returned to, and remained at, undetectable levels.

    4. The higher the final concentration of animals producing Ammonia and Nitrite will be in your tank, the more “powerful” the biological aspect of your ongoing filtration system needs to be. Biological filtration can be researched online and is an important section included in most of the general aquarium keeping books.

    5.Bacteria are responsible for maintaining the cycle. Sterile tanks which are constantly “broken down” and “cleaned”, over sterilized through equipment, or under stocked with bacteria due to constant filter media replacement kill the bacteria responsible for maintaining the Nitrogen Cycle. These systems also tend to be instable with respect to the Nitrogen Cycle. These bacteria will colonize naturally and no starter culture is required in most, but not all, cases. Adding a starter culture can help finish a stalled cycle, but will generally not speed up or help in any other way. While it is not usually important to add bacterial starter cultures, it is important to add the nutrients required for the bacteria to feed, live, grow, and reproduce so they can colonize the tank. These nutrients are, of course, the very byproducts in question, Ammonia and Nitrite.

While there is a lot more to the nitrogen cycle, stocking, and filtration than this, this is all you really need to know to start and cycle a tank and keep it running. There are a number of ways to start and complete the cycle in your tank, and this is the purpose of this article. While it is difficult to avoid being preachy about it, there are methods used and recommended by many that are needlessly cruel, sometimes ineffective, and sometimes detrimental. With this in mind, please approach the subjects offered and consider the facts presented before you decide which method will work for you. There are good and bad points to most methods, so you really need to weigh them out and decide what will work best for you and your fish.

The most common method by which new aquarists cycle new tanks is inadvertently through the mass introduction of new fish, and their subsequent replacements, and the replacements’ subsequent replacements in newly set up aquaria. This is the blind way in which most of us have entered the hobby, sanctioned by the “experts” at our local fish stores. The problem with this “method” is that it can become extremely frustrating, and needlessly expensive, for the aquarist, and is definitely cruel to the fish and/or other organisms killed during the cycling process. Tanks using this method may never completely cycle until the aquarist gets fed up after many months and stores the tank dry in their garage until the next garage sale. While the fish do provide an initial nutrient load, the constant die off, and reloading of nutrient sources into the system, leads to instable bacterial populations that constantly explode, die back, and explode again. The “clearing” products offered by unscrupulous or unknowledgeable retail store representatives to solve this “clouding problem” for the fledgling aquarist are nothing more than money making schemes. In some instances, these products are also counter productive in that they will actually kill off the very bacterial colonies that should be encouraged to populate, leading to a repeated cloudy/clear circle that does nothing to help keep the poor fish subjected to this unstable environment healthy. Fish stocked in such tanks are routinely dying and/or diseased. Yes, at some point, usually when the tank is left alone for a period of time, things can become stable. Unfortunately, this is usually the point at which another massive load of fish is added, starting the entire process over again. Another consideration when cycling in this manner, or the one following, is that utilizing quarantining becomes a moot point. Disease can be introduced into an aquarium with any fish, including those used for the process of cycling.

The next most common method of cycling is to use “feeder” or other such inexpensive fish to provide for the initial nutrient load. While this can work, it is still harmful to the fish used, and is usually not done in such a manner as to provide consistent results. For instance, as the fish die off, they are removed, leading to less and less nutrient production. So, Ammonia can indeed spike and reach unreadable levels, but such levels may be consistent only with the nutrient load of the last fish or so left alive in the tank, not the initial dozen or more that were added. What this can amount to is something similar to the new aquarist buying fish after fish after fish. Upon the initial introduction of long term inhabitants, the aquarist may discover that Ammonia begins to rise again. While this is not a foregone conclusion, it is very common. To avoid this, the aquarist who has cycled with fish should proceed very cautiously in their stocking plan, adding only a fish or so at a time, commensurate with their final “cycling fish” population. As plainly as can be stated, if you have three 2 inch fish left at the end of your cycle, you can only safely assume that the current biological filter can immediately support three 2 inch fish.

While fairly common up until a few years ago in the case of more experienced aquarists, the next method is falling out of favor with marine aquarists, although freshwater aquarists still seem to be using it as frequently as before. This method is called Ammonia Dosing. What is involved here is the procurement of a pure Ammonia source. Several labs and biological supply houses will have pure Ammonia available. It is extremely important to make sure that this Ammonia is pure and free of any and all dyes and perfumes. There are several sites and hundreds of individuals online who use this method and can recommend sources for pure Ammonia if you’re interested. All that is involved is the introduction of Ammonia in the amount of 5ml/day per 10 gallons until Nitrite becomes measurable on your test kit. At this point, you reduce the amount of Ammonia introduced to 3ml/day per 10 gallons until Ammonia and Nitrite have returned to 0 parts per million on your test kit. Finding a source of pure Ammonia may prove difficult for some. Others find the chore of daily measuring and dosing to be unpalatable. This method, however, does offer distinct advantages over using fish, knowingly or unknowingly, to cycle the tank. First and foremost, Ammonia dosing does not harm any animals. Second, the constant measured introduction of Ammonia is preferable to the fluctuating production of ammonia possible in the prior two methods. With a little effort, a perfectly stable aquarium can be reached without ever having had any animal or plant life knowingly introduced.

The last method can be accomplished in a number of ways, but all amount to the introduction of organic matter in order to produce the nutrient loads necessary. The most common way to approach this is through the daily feeding of an empty aquarium with fish food until the cycle is complete. Apart from this having the potential of becoming expensive, it can be very difficult, especially for the beginning aquarist, to judge exactly how much to feed. Constant changing of the amount of food added can lead to fluctuations in the bacterial population similar to what is seen in the first two examples of cycling above. More preferable is the introduction of a mass of organic matter, allowing for the slow decomposition and “time release” of nutrient ammonia as a byproduct. This is usually accomplished through the introduction of one medium sized cocktail shrimp (cooked or raw) per 50 gallons of aquarium water. The cost of a single raw shrimp is usually less than 20¢. This method is the easiest, by far, and is as reliable as Ammonia dosing in producing a cycled tank. In the absence of shrimp, or for those looking for alternative organic sources, fish flesh, shellfish, etc. are all suitable. Using dead fish from other aquariums might seem like a reasonable alternative, but they should not be used. Even a dead diseased fish can introduce undesirable organisms into a tank.

There are several things that the aquarist needs to know that are the same for all methods. Through all methods, Ammonia and Nitrite need to be measured at least every other day, but preferably on a daily basis. Ammonia should spike at around 3-5ppm. Usually this is followed by a Nitrite spike of 2-5ppm several days later. Once both Ammonia and Nitrite have returned to 0ppm and remained there for at least a week, or better yet two weeks, the tank can be considered cycled and stocking with fish can begin. Some tanks may experience a “stalled” cycle where Ammonia and/or Nitrite remain detectable, usually at the same level, for a week or more. If the concentration tested remains the same for this long, it may be beneficial to add either a commercially available “cycle” product containing bacterium cultures, or used filter media or substrate from an established aquarium. In the case of marine aquaria, Live Rock can also be considered. There are some bacteria that can live in both fresh and salt water, but in the interests of producing the best results as quickly as possible, preparations marketed for the cycling tank type should be used. If filter media or substrate from an existing tank is used, either should come from the same type of tank as the cycling tank. If, however, the levels of Ammonia and/or Nitrite remain at nearly undetectable levels, it may be prudent to test the results against another test kit, preferably of a different brand. If the aquarist doesn’t want to go through this trouble, most aquarium shops will test their customers’ water free of charge.

Regardless of method used, the most common question asked by beginning aquarists is “how long will it take to cycle?” The answer, if not desirable, is very simple: until it’s done. Typically, a cycle takes anywhere from 2 to 8 weeks. Shorter or longer cycles are not uncommon enough to be called rare, but there are some issues to consider. First, one should verify the accuracy of the testing kits used. Test kits, especially Ammonia kits, can be unreliable at times, with unreliability becoming more common as the chemicals age. With cycles that seem to have completed in less than 2 weeks, the aquarist should question whether or not the cycle actually occurred and whether or not the result is a stable system. It is easier to test for this with some methods than with other methods. With fish cycling, the aquarist would have to either overfeed for a number of days or intentionally stock more fish into a system of questionable stability. Both methods of testing the cycle can result in the harm or death of the existing inhabitants. With Ammonia dosing, one can simply start from the beginning and attempt to get an increase in measurable Ammonia using the 5ml/day per 10 gallons for a week. If no spike occurs, the tank can be considered cycled. For the last method of organic introduction, one can simply begin adding more organics and measuring for an increase in Ammonia for at least one week. Again, if there is no measurable level of Ammonia after a week, the tank can be considered cycled. With cycles that seem to be taking longer than 8 weeks, the aquarist should suspect a “stalled” cycle. If your tank has not completed cycling in 8 weeks, it would be prudent to introduce bacterial cultures through commercial preparations or filter media or substrate as discussed above.

Once the tank has completed cycling, regardless of which method was used or how long it took, measuring Nitrate becomes a matter of importance. In natural systems that allow for Nitrate to be processed, it is generally customary to view this Nitrate processing as part of the cycle. These would include systems with Deep Sand Beds, those with Nitrate Reductors or Algal Turf Scrubbers, Planted Aquariums, etc. For other systems, the general recommendation is to perform a water change to reduce the amount of Nitrate in the system. In either case, the introduction of fish without first reducing Nitrate to less than 20ppm will most commonly result in algae problems that may continue for months, or even years, to come. Some means of removing or reducing Nitrate should, therefore, be part of a planned regimen of ongoing maintenance before the tank is stocked.

In closing, now that you need to know what you need to know, and what you don’t, proceed with confidence knowing that you made your decision based on what is right for you. Hopefully, you’ll choose one of the more humane methods. Thankfully, these also happen to be the easier, cheaper, and more reliable methods. Good Luck!