What is aquarium cycling

In an aquarium, the same thing happens. You feed your fish, your fish produces waste also known as ammonia , and then bacteria and plants absorb the toxic waste so that the water is safer for your fish to live in. But wait! Where are the plants and beneficial bacteria that can break down the fish waste?

For more details about how the aquarium nitrogen cycle works, check out our full explanation here. There are several ways to cycle an aquarium, and some are easier than others.

Based on our experiences of successfully running hundreds of fish tanks, here are the methods that have worked well for us:. This approach is the most common, used by both beginner and veteran fish keepers alike.

Most people cannot watch an empty aquarium for several weeks or months, hoping that beneficial bacteria are actually growing. So, here are a few tips to help you get started on the right foot:. A water test kit helps you determine if there are toxic levels of nitrogen compounds in the aquarium.

This method is our favorite because it truly transforms your aquarium into a natural ecosystem, both biologically and visually.

Bacteria-1 feeds on ammonia, so we need to add some to the aquarium. We want to dose the aquarium to around 4 parts per millilitre ppm ammonia, this is the first use of our testing kit. There is a common myth that anything above 4ppm ammonia will stop aquarium cycling. Does too big a buffet stop people from eating it?

No, the bacteria will still eat ammonia. If you are using fish food, you will not be able to measure this yet. The fish food will take a few days to break down and produce ammonia. From here, you will need to test the aquarium regularly daily is ideal to ensure that the level of ammonia remains around 4ppm. If it starts to drop, top it up.

Ammonia is the food source for the bacteria we are trying to grow, so we need to keep it in plentiful supply. We are now waiting for our test kit to read some level of nitrite. Detecting rising levels of nitrite means that we now have a growing colony of Bacteria It is eating up the ammonia and producing nitrite as waste. Many new aquarists have an idea that this is an overnight process, but it may be 2 weeks before you see a reading of nitrite.

Sometimes longer. Once you have started to detect nitrite in your tests the waiting continues, so your main ingredient of patience needs to keep working. But this is great news and you are well on the way to a cycled aquarium. Nitrite is eaten by Bacteria-2, so we are now providing food for our second colony of beneficial bacteria. What you need to do here is everything you have been doing up to now.

This means regular tests and keeping the ammonia topped up. As your colony of Bacteria-1 continues to grow, the ammonia level will drop quicker and quicker.

If ammonia runs dry, then Bacteria-1 stops producing nitrite, which means that there is no nitrite for Bacteria-2 to eat, so any Bacteria-2 stops growing.

This will only slow things down. So keep that ammonia level up! Rising nitrates is an indication that we have established a colony of Bacteria-2 that is starting to eat up those deadly nitrites. Nitrates are the end of the cycle in most cases, so a reading of nitrates on your tests is excellent news. You should now be seeing your ammonia levels dropping daily, eventually to 0 within 24 hours, this is exactly what we have been aiming for.

Getting to this stage can often take up to 8 weeks, so patience is critical throughout. The important thing to remember is to keep your ammonia level up. This ensures a constant supply of food to keep that bacteria growing.

There are a few issues that almost always occur whilst cycling, so here is a quick overview of what they are:. When either of the first two issues occurs, the temptation to clean the tank can be overwhelming. But please resist the urge to clean the tank too soon as you could reset the cycle, particularly if you clean the filter.

Both of these issues will be greatly reduced by themselves as your filter develops a colony of bacteria. If you top your aquarium up to 4ppm of ammonia and get a test reading of 0 ammonia, 0 nitrite and rising nitrates within 24 hours for 3 days in a row then your tank is cycled. In an established aquarium, ammonia and nitrite should be undetectable.

Nitrate should be kept as low as possible by weekly water changes, or more frequently if needed. Your tank has cycled to deal with 4ppm of ammonia in 24 hours, or whatever level you chose to cycle it at. So if you add too many fish, they may produce more ammonia than that and be poisoned. The size of your aquarium will dictate how many and what type of fish you can add in total. Adding a small group of small schooling fish, like Tetra, or a single larger fish is a good way to start.

From here, keep testing the water to ensure that your bacteria is coping with the load and slowly add more fish. Leave at least a week in between each new addition to ensure the filter is coping well. If you arent getting any fish for a few days, or longer, you will need to keep adding ammonia to keep your colonies of bacteria fed.

Before adding fish you will need to start maintaining your tank. During cycling, your nitrate levels should have been rising and are probably pretty high by now. The reason for the different readings is due to the way these two kits measure nitrates, I will write this up in more detail and link it here once I have — HERE is the link.

Bear in mind that you are about to add fish. When you do, nitrate will climb, so your readings need to be much lower than the figures above before adding them. To achieve lower nitrate levels, you need to do a water change. Once cycled, your filter is the thing that will keep your fish alive.

So it needs to be looked after. So does the bacteria inside it, without which it is pretty useless. Aquarium shops and filter manufacturers will tell you that you need to change your filter media every month or so. So, keep your filter media until it is literally falling to bits, then change half out at a time at the most. If you change half at a time, at least half of your bacteria colony is kept. Is it the water from your water change that raised the Nitrates to 5?

Just something to be mindful of. I was just reading online. Is that a good thing to do? Baking soda raises both pH and KH. If you are adding it to tanks with fish, go slooooooow. Add a bit, wait, test and repeat. I looked at the spreadsheet and the nitrates actually went up from 1 to 5 the day before my water change. I was thinking of putting baking soda in the empty 10 gallon tank to try to raise the PH in hopes of moving the cycling along faster. Increasing the pH to an appropriate level should noticeably improve the speed that the tank cycles.

Please let me know how it goes. I read over your article again. Is that correct? What you read is correct. Nitrites are supposed to spike before the second bacteria grows in number to accommodate the nitrites being produced by the first bacteria. As long as you are providing a consistent source of ammonia, they will balance themselves relative to this input.

You just have to wait. Make sure you keep an eye on the pH, as it will decrease over time. Nitrites and nitrates are acidic. Water change or add more baking soda as needed. Over the next few days pay attention to what is happening with the nitrites and nitrates, one of the two or both will go up. This is a good thing, and means you are back on track.

To help with testing, view the tests outside in daylight, in the middle of the day. It will allow you to better observe the actual color against the chart. Thanks Ian, I needed that pep talk! I really want to have Izzy and eventually her babies in the big tank so I can start enjoying them. I will keep testing and watching and let you know how it goes. I sincerely appreciate the information and advice you provide here.

My 10 gallon tank is finally cycled! Now all I have to do is a water change for the nitrates I did want to ask about transferring my fish from the 5 gallon tank to the 10 gallon one. I think you said one fish would be ok to keep the bacteria going, correct?

Even though her readings are zero ammonia and zero nitrites every day in her 5 gallon tank? Just want to make sure. And as I understand it, the amount of bacteria will adjust as I gradually add more fish, correct?

Also, the 3 gallon that the babies are in. And it has never shown any nitrites or nitrates. The PH is very bad. It worked very well to raise the PH in the empty 10 gallon tank. The 3 gallon tank has a small heater, but with no settings. It keeps it at about degrees. I would like to keep trying to cycle this tank to use to put new fish in for a week or two before putting in the big tank.

A single fish, such as a betta, will easily keep the beneficial bacteria going. In which case you can acclimatize your fish the same way you would when you buy them from the store.

Based on what you have told me, I would say the pH is more of an issue, going off how the cycle completed once you rectified the pH in your 10 gallon. It seems plausible this tank is having the same issues with the pH of 6 and it will need to be raised in order to cycle. I read over your KH guide. I guess I should go ahead and order the test kit.

Aquarium water generally becomes more acidic over time — even if you have not made any changes. Part of this is because nitrites and nitrates are acidic. Most people can stay on top of this with regular water changes, which are enough to balance the KH and pH.

I think I must have been unclear about a couple of things because of so many tanks and fish, sorry. She has been in a new 5 gallon tank since the babies were born 2 weeks ago. She has 0 ammonia and nitrites so far.

So I wanted to make sure she would produce enough ammonia to keep the bacteria going. Could it be, cycled even though nitrates have never shown up? I guess I could skip putting Prime in for one day and see if the bacteria is still gone the next day. So you said before to go slow with baking soda when fish are in the tank.

Do you think it would be better to test the kh and use the thing you mentioned in that article if necessary? Absolutely, ignoring that platies are considered to be best kept in groups, a single platy will produce ammonia and the beneficial bacteria will balance out accordingly.

If the tank is cycled, they will be fine in a tank that size. After all, in the wild, their home is much bigger than 10 gallons. As for when to add the mother, it all depends on the growth rate of the babies.

Depending on conditions food etc, they can grow at different rates. In an empty tank, baking soda is fine. Beginners can easily calculate how much they need, so as to not cause rapid raises that will shock their fish. Baking soda is a more trial and error as to how much you should add. But it still works! The ammonia always stayed at 1 or 2 when the mother was in it. I think the low pH has something to do with it.

Your larger tank was experiencing similar, when we first started troubleshooting, right? Even so, I am puzzled as to why you are not noticing a spike in ammonia. Unless you use a filter media that removes it, it should begin to increase.

I think the first step is to increase the pH and then begin trouble shooting from there, adding ammonia manually like you did on your 10 gallon. Ha, yeah you lucked right into that group of platies! Just be mindful that 6 platies is a high bioload for a 10 gallon. The filter is actually very small with carbon inside some mesh. You should be able to catch your fry with your fish net. Oh, one more thing, sorry. Oh absolutely. And I probably will still be asking you questions when I do the 20 gallon one later on.

One thing I totally forgot to ask you, and probably important, is that a white cotton-like substance has appeared on the ornaments in the 10 gallon tank. Do you know what it is and if it will hurt my fish? This can result in all sort of oddities such as white cloudy water, gooey brown sludges and white slimes. Unfortunately, without paying attention to what triggered, these can be quite hard to identify the cause in hindsight. Can you confirm it has appeared during cycling? Thank you.

I had some new aquarium ornaments, so I rinsed those really well and put them in the 10 gallon instead of waiting for the filter to work on the ones I had bleached. I wanted to get the babies moved today. I did the test twice to be sure.

So I really want to get them out and try to raise it. How long after putting baking soda in a tank would you have to wait to put a fish in it? A pH of zero is pretty much hydrochloric acid. You can test this hourly, after two hours or just wait until the morning. So the 5 babies have been in the 10 gallon cycled tank since yesterday, and so far they seem happy.

I did water changes till the nitrates went way down. Others say monthly or at other intervals. Speaking of filters, the one in my 10 gallon has been there for over 2 months while cycling. I rinsed it in the aquarium water when I was changing it and as soon as I touched it, the white part just kind of stretched out in a long piece, kind of like cotton does when you pull it apart only wet and very easily stretched.

I actually had to push it back in to keep it in the filter. Is that normal? You will absolutely lose the beneficial bacteria when you swap out the filter. Especially if your tank relies on the foam in this filter for a biofilter. You can expect your tank to crash if not done correctly.

The razor blade business model should not apply to aquariums. Locking yourself into buying disposable filters for a quick buck, at the cost of fish health and lives is disgusting.

My recommendation is a biomedia say ceramic rings and mechanical filtration combo sponge and if required, filter floss for clarity.

So if yours did, most of your beneficial bacteria will be hanging there instead of the wool stuff. In your filter, if you have no ceramic rings, then that cotton wool like stuff will hold a good amount of your bacteria. As for how long these last. Ceramic rings and good quality sponge can last years before needing to be replace.

A good sponge should be able to be cleaned with three squeezes in siphoned tank water. Purigen is chemical filtration, which is a which is separate from biological beneficial bacteria and mechanical sponge filtration. It also can absorb tannins. I have a personal dislike for the stuff. There is a tendency to rely on purigen instead of good tank practices, which generally eliminates the need for it altogether. I see purigen as an emergency solution rather than an ongoing tank addition.

Let me know if anything I have said needs clarification. Of course, as usual I forgot to ask you something. What do you think of Purigen. Is that good to use in my filter instead of the spongy thing I mentioned? I just looked at both of these. Which would I use? My filter is your average hang-on-the back filter. The package said it helps capture ammonia. So I should leave the old cottony filter there for about a month to spread the bacteria and add the rings and sponge, right?

Then take the old one out after a month. Do you think I should look at buying a better filter that will house everything I need? If so, what kind of filter would be best for my 10 gallon tank? It probably contains something like zeolite. I would only recommend the pre-filter sponge if there is no room inside the filter for mechanical filtration. Loose is generally cheaper buy a drawstring filter media bag to house them but the end result is the same.

The only difference is that with the loose, you can swap them out, half at a time say in two years, when they eventually deteriorate this way the bacteria in the old ceramic rings will colonize the new rings, without causing a causing a complete crash. After two weeks, swap out the other half. For a HOB, aqua clear filters hit the sweet spot in price and ability to hold everything you need.

If memory serves correctly, it comes with ceramic rings too. The easiest way in this case to colonize the new filter is to run both HOB at the same time for weeks, before removing the old one. I looked online and it looks like the aqua clear filter you mentioned does have ceramic rings, as well as carbon filter insert and foam insert. You are saying to run the new filter and the old one at the same time for a few weeks, correct?

Do you know how I can do that? Am I essentially cycling the tank again with the new filter? If you only have a single cutout, open the filter up and remove any places where beneficial bacteria could be such as the cotton filter and place it in the new filter on top of the ceramic rings. Running the new filter now will have the same effect. Keep testing and keep prime on hand, just in case, you may experience an ammonia spike.

As for how it works. In a new tank there is no bacteria. When you cycle, you are not just waiting for two different types to appear, you are waiting for them to multiply.

So to put it really simply, first there is 1 of the first bacteria. Then there is 2. Then there is 4. And so on. Repeat for second type of bacteria. You already have an entire colony of both in your tank right now. It takes a fraction of the time to cycle with a tank with a pre-cycled filter.

If you have a good local fish store, they may even sell pre-cycled sponge filters for this very reason. Is there a way to take it apart and submerge it? But I know you mentioned the ceramic rings can last 2 years.

Sorry, I could have been more clear here. Simply leave the whole filter, minus the bits mentioned, submerged in your tank.

If and when it happens, you simply replace them with a better quality biomedia, one that will last much longer. Squeezing it out in tank water until the water runs clearish will unclog it. It should last more than 2 months. Again, if it does wear down, simply replace it with better quality stuff. Carbon is the only part they have right. Carbon is a chemical media, it absorbs tannins and bad smells among other things. Or just some part of it?

All good, I could have been clearer here. You want to submerge as much of the section that water flows through as possible. Depending on the design, this will vary as to how simple it is to do this. The ideal however, is to run both at once. Just had a thought, when you say cutout, is the lid removable? If so, just remove the lid for the duration and add the second HOB.

It was 6. We were messing with the tanks, water changes, ornament changes, testing, etc, all afternoon and I was stressed, frustrated, and tired. Apparently I read 0 instead of 6. And if so, how much? Once your tank is cycled, I recommend that prime only really be used in an emergency, such as an ammonia spike, outside of dechlorinating water.

Prime hides the problem rather than solve it. Yes, the lid is removable. So having the entire top open is ok, right? I guess I could always put some kind of net or screen over it.

And you said to leave the old filter running for about 3 or 4 weeks, correct? For the short term, say cycling your second filter, removing your lid is the easiest way to go about it. If you really are concerned, or notice behavior that suggests jumping, cheese cloth or something similar is cheap and can act as a barrier. Leave the old filter cycling for 3 or 4 weeks alongside your new one to be safe. Afterwards, remove the filter cartridge and sit it on top of your ceramic rings in the new filter.

Safe sounds good to me. So I will do exactly as you suggest and run both filters for a few weeks. How often would you test the water in a cycled tank with babies? How often to test your water? Once your tank has cycled, and you have your fish in. I suggest testing every day, so you can see how chemicals such as nitrate and pH change across a week in your tank yours will be different to mine or anyone elses Once you have a good understanding of this, you can swap over to testing with your weekly water change.

And of course, if you think something is amiss outside of your testing routine then by all means, test! Oh, one more thing on the filters, monitor the flow. Two filters can produce much more current than one. When the babies were still in the 3 gallon, I was testing both tanks every day because I was worried about ammonia and niitrites harming them, and wanting to see if the 10 gallon was cycled.

I did read something about how the filter current can sometimes be too strong. I wanted to ask if I should cover the aquariums if they are exposed to bright sunlight.

I read that sun can cause algae to grow, but my question is really about the fish. The babies are still doing well in the 10 gallon tank, as is the mother in her 3 gallon tank. I bought the AquaClear filter you suggested and will probably install it tomorrow along side the old one.

Your primary concern here is algae. An aquarium is an enclosed setting, and we want to control each variable. Direct sunlight adds an unknown to the equation. I installed the second filter today at the lower flow speed. I thought if both filters were at one end, the other end of the tank would be calmer for the babies. Also, since we have the 10 gallon cycled and things are going well, I wanted to ask about the 3 gallon again. I threw my calendar away but I know it was late October when I started that tank.

The readings every day are still 0 nitrites and 0 nitrates, ammonia around. How can that be? The ammonia has at times been 2. Do you think I should put some quick start in it? I sure would like to get it cycled and stop having to dose it with Prime every day. This impacts how much oxygen will be in the tank, and since your tank is a little overstocked, this is important.

You are going to have to remind me of the 3 gallon, does it have a filter? Is the pH at 7? What is the temp like? Yes, it has a very small filter, and the temperature is about 77 or 78, it has a small heater too but not adjustable. The PH was 7. It has sometimes been lower, but for the most part it has been good.

Can you you do a water change and confirm your nitrates again? As I understand, your tapwater is 5 PPM, so some level of nitrates should be showing up.

I was sick for a few days. Nitrites at. Just wanted to let you know. I have my fingers crossed that this is the home stretch! One quick question. Do you dose with Prime the same way which would be 2 doses if there are only nitrites and no ammonia? Thank you Ian!!!! Yes we did a fishless cycle for the initial set up. It took about 4 weeks. I guess this is a process with a huge learning curve but I have got to get rid of that mildew smell!

Did you test your water parameters ammonia, nitrites, nitrates, pH with an aquarium test kit? This can often help narrow down the cause of problems, in this case the smell. My nitrites are at 2.

Does that mean I have to start from step 1 again? Or do I keep dosing the half doses until the ammonia starts to rise again? Thank you so much! You want above 1 ppm in your tank so that the first beneficial bacteria that converts ammonia to nitrites doesnt starve. Just keep dosing with ammonia so that it reaches readable levels. Every time it dips below 1 ppm add more. High, thanks for taking time to help I have been cycling my 40 G saltwater tank for over 3 weeks now with no luck.

Are you sure you are doing the tests right? I only ask because I have had seen three people now incorrectly administer their nitrite and nitrate tests. This was the reason their ammonia was dropping but they were not detecting nitrite or nitrate. Good work! It sounds like you are all over the testing, so we can narrow that down. Are your salinity levels in order?

Hi, thanks for helping Salinity is , pH 8. Pink algae? Once your nitrite levels have reached a certain point a bacteria called Nitrobacter will develop.

When the levels of nitrite and ammonia reach 0ppm parts per million , your tank has been cycled. There are two methods you can use to maintain acceptable levels. This will also benefit your tank by removing substances such as DOCs dissolved organic compounds , solid fish waste and replenish dissolved materials that your plants and animals may need. If you own a freshwater fish tank, you can add aquarium plants can help use up some of the nitrates.

Own a saltwater tank? Let me start by saying, this is not the preferred method. However, some species can handle it better than others. Your aim is to populate the tank with fish that produce waste. But can also survive the high levels of ammonia and nitrite long enough to allow for the beneficial bacteria to grow. You should add approximatley fish per 10 gallons of water.

Adding too many fish will lead to excess waste. This can cause an ammonia spike and kill off your fish. Here are a few good choice for cycling fish :. Feed your fish sparingly, be careful not to overfeed them. As a general rule of thumb feed your fish once every 2 days. And only provide them with moderate-sized meals.

This increases the level of toxins in your tank before the good bacteria is able to colonize your aquarium. And you feed them smaller meals because leftover food will rot and produce even more toxins! Your fish are being exposed to potentially lethal amounts of ammonia and nitrate, so regular water changes are a must.

Make sure you add de-chlorinator to the water. So keeping track of the amount in your tank will help you manage your fish throughout the process. Testing for nitrate is a must have. After each addition, wait for about a week and test the water again. If the ammonia and nitrite levels are still low, add some more. Adding too many fish will cause the ammonia and nitrite levels to rise.

This will stress your fish and can lead to disease. This is the method I would recommend you use. I would like to add, there are other methods to doing a fishless cycle.

You have no fish in the tank, so what do you do? A nice simple way to do this, is to begin by dropping a few flakes of fish food into your tank. Add the same amount you would if you were feeding fish. You can do this every 12 hours.

Now, all you have to do is wait. The flakes will begin to decay — releasing ammonia into your tank. Test every other day, and try and maintain the ammonia levels at 3ppm. Nitrosomonas will begin to grow and start consuming the ammonia. You can use a commercial test kit for this. Once the ammonia and nitrite levels have returned to zero, the cycle is complete.

Again, don;t just go adding a load of fish. You need to do this gradually. And wait at least a week or two before introducing more. Consider cleaning any substrate with a siphon or hose before adding fish. Yes, the nitrogen cycle can be sped up. Filter media from an established tank will have nitrifying bacteria attached. If you have access to an established tank which uses an undergravel filter, bacteria will be attached to the gravel. This will have the same effect as using media filter.

Take roughly a cup of gravel and hang it in a mesh bag in your filter, if you can. Living plants , not fake plants, can help to introduce bacteria to help nudge the process along. Especially, if you get them from an established tank. Plants use a process called protein synthesis to moderate the ammonia levels in your tank.

Pro Tip: Using fast-growing plants like Vallisneria and Hygrophila will help absorb more ammonia. This is important, a HUGE downside of using an established tank to speed up your Nitrogen Cycle is that you could transfer some nasty stuff. You can shorten the time. But, testing the water, performing water changes and regular maintenance is essential if you want to be a successful hobbyist. Here are some common problems you may experience and how you can combat them.