A Simple Approach to Fishless Cycling
By Rebecca Townsend
So what exactly is fishless cycling? In short, it is a manufactured reproduction of the nitrogen cycle that would otherwise occur naturally in a new aquarium in which fish are added. Unfortunately, this cycle is very stressful for the fish in question though, as both ammonia and nitrite is very toxic at detectable levels. That's why alternative methods have been developed, so we can attain the bacteria needed to keep our fish in a safe, healthy environment without harming any fish in the process. In this article I will attempt to explain the process of fishless cycling in a simple, easy-to-understand fashion that even a brand new hobbyist can understand.
I will not go into great detail about the nitrogen cycle here, for that is not the intent of this article. Instead, I will just give you the bare minimum that you need to know to understand how this process works. Fish, as well as any other living or once-living thing that can be found in an aquarium, produce waste in the form of ammonia. Bacteria forms which converts that ammonia to nitrites. More bacteria is then formed which converts the nitrites into nitrates, which is the least toxic product of the nitrogen cycle. Once you have measurable nitrates and the ammonia and nitrites are gone, then your cycle is complete. The bacteria responsible for this process are what we are trying to achieve here. That's the stuff that will break down the toxins the fish produce and make the water safe for them to live in.
So, are you still with me so far? Now that we have established what we are trying to do and why, the next step will be how. There are many methods of fishless cycling available, but I like to use the simplest and most direct route available - pure ammonia. You can find it in most grocery stores or hardware stores, usually with the cleaning supplies. But make sure whatever brand you choose is 100% pure, clear ammonia with no color or any other additives. If in doubt, pick the bottle up and shake it up. If it foams or forms any suds, don't use it. You will also need some water test kits, found in your local aquarium supply store or many mail order pet supply companies. Test kits are invaluable in the fishkeeping hobby, and you will find yourself using them for much more than just the tracking of your fishless cycle. The three you will need for need for now are Ammonia (NH4/NH3+), Nitrite (NO2), and Nitrate (NO3).
By now you should have your aquarium filled with water, gravel or whatever substrate you intend to use, and have your filter up and running. Your tap water will be best for cycling purposes. If you feel you need to modify your water to fit the type of fish you want to keep, there will be plenty of time for that after your cycle is over. If you have chlorine in your water, you can simply let your water sit overnight and the chlorine will outgas by itself. But if your water company also adds chloramines to the water supply, you will have to remove them yourself. You can do this by boiling your water, and let it to cool overnight to allow any by-product chlorine to outgas and to let oxygen back into the water. Or you can add a dechlorinator that also removes chloramines. It's best to use a simple one without the extra additives, to avoid any false readings from your test kits. Also make sure you don't have any ammonia-removing materials in your filter, such as zeolite, ammo-rocks, or nitra-zorb. These will seriously deter, or possibly stop, your cycle. If you have a heater, it would also help to set it to around 86 degrees F. The warmer temperature increases the metabolism of the bacteria you want to create, thereby speeding up the cycle of your tank.
If you have access to another disease-free established tank, this would be a good time to add some seeded material to jump-start your cycle. See if you can obtain a cup or two of the top inch of gravel from that tank, as this is where the majority of the bacterial colony lives, next to the filter material. You can either add it directly to the top of your new gravel, or in a filter bag or clean stocking if the color doesn't match and you want to remove it later. If you have room in your filter, you can put the bag of established gravel right in there. Even better than old gravel would be any old established filter media, such as a cartridge, floss, or foam. You can even add filter squeezings from an established filter directly to your new one. Or clean out all that gunk at the bottom of the established filter's chamber or impeller, and put this gunk directly into your new filter. All of these materials contain the good bacteria you are trying to establish, so the more of it you can get into your new tank, the faster your cycle will go. In fact, if you can also re-seed the tank every couple of days as your cycle progresses, that would be perfect. Just make sure the tank you are borrowing from is disease-free.
If you don't have access to another tank, see if your local fish store will let you have some used filter material or squeezings from one of their disease-free tanks. Sometimes they will even let you have a small amount of gravel if you ask nicely, or maybe for a small fee. But don't let them sell you any of the bacteria-in-a-bottle products. These pre-packaged products that promise to cycle your tank are nothing other than a placebo, as the bacteria required for nitrification are aerobic and have no dormant stage, so cannot be stored in a jar or other container. But if you don't have access to any other tanks at all, don't worry about it. You're cycle will still be established even without any seeded material at all.
Now you are ready to add the ammonia. This can be as simple or as complicated as you want it to be. Some people have reported good results by simply dumping some in the tank water to read around 10ppm, then waiting till the ammonia and nitrite readings were back down to 0 and nitrates were showing a positive reading. While this is certainly going to work, I'm not sure how large a colony of bacteria will be left at the end of the cycle. By adding ammonia on a regular basis, you can be assured of a large colony of bacteria to support a full load of fish at the end.
The amount of ammonia you add initially is going to be by trial and error. Different brands have different concentrations, so you'll have to find out for yourself how much you need. But add enough to read anywhere from 2ppm to 5ppm on your ammonia test kit, and keep track of that amount. I like to use a child's medicine syringe or dropper for this. This is the amount you will be adding on a regular basis, say every day or even two or three days. As bacteria colonizes and multiplies, it will consume the ammonia and begin to convert it to nitrite. Be patient as this may take several days, or even a couple of weeks, for the nitrites to show up. And don't be alarmed if your ammonia readings go higher than your test kit chart shows. This is a normal process and it will come back down when it's ready.
When your nitrites show a reading of around 3-5ppm, cut the dosage of your ammonia additions in half, but keep adding it at the same regular intervals. You need to feed the bacteria to ensure that it keeps growing and multiplying to form a full bacterial bed. If you stop feeding the bacteria, they may begin to die back to fit the food source. This nitrite phase is usually the longest part of the cycle. And again, don't be alarmed if the test readings go off the chart. More food equals more bacteria.
This phase also often seems to get "stuck". If your nitrites seem to be off the chart for more than a couple weeks, with your other readings seeming to be at a standstill also, it might be time to do something a little different in your routine. Maybe skip a couple ammonia additions if you are adding every day, or add an extra one if you are adding every couple days. Or try adding a different amount, maybe a little less. You could turn up the heat a little, just don't go over about 90 degrees F, as you don't want to cook your bacteria. The point is, whatever you are doing routinely, just do it a little different for a few days to shake things up and get your cycle rolling again. If all else fails, do a small water change of maybe 20%, but don't touch your gravel or filter.
During this second phase of the cycle is usually when nitrates begin to appear and ammonia drops back down to 0. But every tank's cycle seems to run a little bit different due to all sorts of factors which could include seeded material added, heat, light, concentrations of ammonia, and I suspect the chemical makeup of our tap water. So it's not unusual to show readings of all three components at the same time, or two, or even one at a time.
The thing to watch for is when you have a positive reading of nitrates, and your ammonia and nitrites have both dropped back down to 0. If you have achieved this, you are ready for a large water change. If your nitrates are below 40ppm, do a 50% water change. If your nitrates are over that amount, do about a 90% water change to bring them back under control. Then add your original dose of ammonia, wait 24 hours, and run your tests again. If ammonia and nitrites are still 0, congratulations - you are finished and ready for fish. Just don't forget to readjust your temperature to meet the fish you want to keep, and give the heater enough time to stabilize.
This method of fishless cycling is usually quite a bit faster than cycling with fish, but it can still seem like forever when you are looking at an empty tank full of water. With a lot of established material to start with, it can go as fast as just a couple of days. On the other hand, with a completely sterile environment to start with, it can take as long as a couple of months, depending on the concentration of ammonia, heat, etc. The important thing to remember here is to relax and be patient. The whole point of this method is to provide a safe and healthy environment for our fish to live in. And if you get impatient or nervous because your test numbers seem to high, just remember the part about being patient. You're not hurting any fish! And you're certainly not going to hurt a box full of water with a little ammonia. Besides, a bottle of ammonia is a lot less expensive than fish, and can cycle a lot more (and bigger) tanks than just one fish can.
Take this time to research the kind of fish you would like to have. And if you also want to have live plants, this would be the perfect time to do a little aquascaping. Plants will consume the nitrates and help to keep them under control, and provide extra surface area for nitrifying bacteria. As an added bonus, they will also bring in bacteria of their own, the same kind you are trying to establish, as long as you don't let them dry out or rinse them in water containing chlorine. If you feel you must rinse them before putting them in your tank, do so in dechlorinated water to protect the bacteria.
So what are you still reading this for? Go get your ammonia and create that perfect new home for your fish. Remember this is not an exact science, so don't be afraid to experiment with it to see what works for you. Relax, be patient, and have fun with it!
Here's wishing you a lifetime of healthy, happy fishkeeping! Rebecca Townsend