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Fishless Cycling: The who's, what's, when's and why's
By: Curt Lemrick



In the limited time that I have been involved as an aquarist, I have heard literally hundreds of opinions, philosophies and preferences for every aspect of the hobby. Why the differences though? Much of what our hobby is based on is science, but as we all know, the number of variables is unnumbered. In know what can each of us control each variable in the same way, hence, different experiences. What I am going to talk about, is the science of fishless cycling, and in turn the experiences that I have had using it.

Just as an introduction, my name is Curt Lemrick, I have a B.S. in Environmental Science and I am a second year student at Iowa State College of Veterinary Medicine. I am interested in small animal private practice and fish. In no way am I a fish doctor, although that is my goal, and maybe in 3 more years that is where I'll be. So take this article with a grain of salt. I am in no way an expert, merely an enthusiast that has done much research.

Before I get into the nitty gritty details and how to's, we need to understand why anyone would want to use fishless cycling. If you have found this article you probably know what fishless cycling is. If not, very briefly put, it is the addition of fish waste products to a new aquarium to stimulate the nitrogen cycle before the actual addition of fish. I'll explain in more detail later.

Respiratory cycle
photo from Rolf C Hagen Inc.

If your goal is faster cycling or larger bioloads, I'm afraid you may be disappointed. Fishless cycling is not designed for this, and rarely can either of these be realistically achieved any better than traditional cycling. Both require a certain amount of time. However, there is one main difference. Here is where I get into my philosophy, so bear with me, but I really think you need to understand this to justify your use of this method. Fish have rights. Just like any living animal which is in our care, that animal was at one point, whether domesticated or not, taken from its natural environment. At that point, we took on the responsibility as aquarists to provide a suitable and favorable environment for our fish. One way to do this is by utilizing fishless cycling.

Have you ever gotten a new tank, set it up, put some fish in, and battled dangerously high levels of ammonia or nitrite for a month? Well it happens and its frustrating. But think about the fish that are in there. That is there home. What if we pumped carbon monoxide into your home for a month. You probably would not fair well. Same concept. So as well as helping the fish, this will help you in the long run as far as keeping healthy fish for life. Large public and private aquariums use this process to minimize health risks to their fish.

A major opinion that I have run into is that fishless cycling is unnatural. These people say that adding "chemicals" to your aquarium is wrong. Well, certainly subjecting your fish to high levels of ammonia and nitrite is not natural. Do a little environmental research and test any fish bearing pond. See if you ever find levels as high as in a cycling tank, or even any at all. Well, you won't. So do not let anyone discourage you with this argument, it is invalid.

;Now enough about the philosophy and why to use fishless cycling. Let's discuss how to use it. First of all, allow yourself at least as much time to cycle your tank as you normally would. In fact, if this is your first time, you might want to plan on more time, because mistakes are almost inevitable and can slow the process down. But don't worry, it just takes a little practice. Secondly, you need an aquarium that is ready to cycle. This means completely ready to go. An appropriate biological filter, all water parameters where you want them and stable etc. Once this is established you are ready to go.

Now, you have two choices as the ammonia source. You can use ammonium chloride(NH4Cl) or ammonium hydroxide(NH4OH). I will refer to these as A-Cl and

A-OH respectively to simplify things. The method I use is for a pure ammonia source only. So don't go down to the hardware store and buy a bottle of ammonia. This kind of ammonia is usually A-OH, and is usually very dilute, making it hard to judge the amount to add. On top of this, these are sold as cleaning solutions and often contain scents, dyes and surfactants, all of which are detrimental to your aquarium. Therefore, use ACS or reagent grade granular A-OH or A-Cl. I say use granular because when using a liquid, it is harder to measure because as it ages, the concentration changes much more than granular ammonia. You can buy either of these at any lab supply store such as, Inc. or a similar site.

The main ingredient we are interested in is ammonia. Unfortunately we cannot get this without the hydroxide or chloride attached. My advice for most freshwater aquariums is to use A-Cl. This is because A-OH is a base. When added to water, it disassociates and OH binds alkaline metals, that are naturally in your aquarium as alkalinity (ie calcium and magnesium carbonate). Carbon dioxide will ultimately be produced and acidify your water.

I received this from a reader, as I am not a chemist or the original author I will post it here with his links to read for yourself. "This, the underlined section, is incorrect. Hydroxyl ions (OH, that is) don't 'bind' to carbonate compounds when they dissociate (not 'disassociate', BTW). They stay in solution, at least ideally, as when we add them (as in CaOH) to reef aquaria for just this purpose -- to raise the pH. Nor is it clear how CO2 could possibly be produced here. Perhaps (probably) you have OH confused with H (hydrogen ions) which are liberated upon the addition of acids (not bases) to certain aqueous solutions. Consider reading here and here "

A-Cl will disassociate to form and chloride will readily bind to other ions in the water such as sodium etc., and rarely will bind to OH-. Therefore you can expect your pH to remain stable, or at most slightly acidify. I am not a chemist, but this is in a nutshell what happens. The process is not important, just the effect.

Now you know what to use, so here is my "recipe". This is the general guideline that I use, and works for me. I originally adopted this protocol from an associate who is a chemist at the Tennessee Aquarium.

1. Use ammonium chloride, not ammonium hydroxide. Ammonia hydroxide will bring your pH too low and cause you to lose alkalinity and likewise your bacteria population. NH4Cl is available from pretty much every chemical company at a reasonable price.

2. Your target concentration will depend on your expected bioload. The higher the load the harder you should spike the water to create a bacteria population that is sufficient. Never start out with more than 1 - 2 ppm and watch your nitrogen cycle and may be necessary to change water if your pH crashes drastically. 0.011 grams of ammonium chloride per gallon of tank water will achieve a 1ppm level.

3. Spike the tank once at 1 - 2ppm (1.5ppm is a good target), let it cycle through almost completely and then spike it again. You can use a slightly higher concentration the second time if you think your bioload will be large in the tank. You can even spike the tank a third or fourth time depending on your timeline and expected loads.

4. You will know that you have finished your cycle when all of your ammonia and nitrite levels are 0 and your pH has stabilized. The tank should be able to cycle through the additional doses of ammonia chloride within a couple of days of addition if bacterial populations are sufficient. The whole process usually takes 2 - 4 weeks depending on temperature, filtration and dose rates.

I hope this is helpful and you use it to create a more healthy and successful environment for your fish. Please feel free to address any questions, comments or discussions on Badman's Tropical Fish message board.




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