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Discover the ins and outs of fish-in cycling to ensure a safe and thriving environment for your aquatic friends. Follow our step-by-step guide and expert tips to make your fish-in cycling journey a breeze.
Oh no!
You've just brought home your new fish and only now discovered the importance of cycling...
Or perhaps you've been misled by a pet store employee who claimed that running your filter for 24 hours is sufficient before adding fish.
Worse yet, maybe you accidentally wiped out the beneficial bacteria in your tank and need to start the cycling process from scratch.
Don't fret! These situations are more common than you'd imagine.
If you can't return your fish, there's only one solution: You'll need to cycle your aquarium the traditional way – with fish already in the tank.
In this article, "Immediate Measures: Your Essential Guide to a Safe and Effective Fish-in Cycle," we'll guide you through the process of successfully cycling your aquarium with fish inside.
If you haven't purchased your fish yet, we highly recommend opting for the fishless cycle, a simpler, quicker, and safer method for preparing your aquarium. Curious? FishLab's fishless cycling guide will lead you through every step.
Imagine this: You’re setting up your first aquarium, and you’ve already picked out your favorite fish species. You bring them home, introduce them to their new environment, and then disaster strikes. Within a few days, some of your beloved fish are showing signs of distress, and others don’t survive. Why did this happen? The answer lies in the nitrogen cycle.
The nitrogen cycle is a natural process in which beneficial bacteria break down harmful substances like ammonia and nitrite, which are produced by fish waste, uneaten food, and decaying plants. Without an established nitrogen cycle, these toxins can build up in your aquarium, leading to a deadly environment for your fish.
Fish-in cycling serves to jump-start the nitrogen cycle, an unseen three-step process where beneficial (good) bacteria establish themselves in your filter, protecting your fish from harmful ammonia.
For a more in-depth explanation of the nitrogen cycle, check out our detailed guide here. If you’re new to the hobby, it’s essential reading since a well-functioning nitrogen cycle is a critical component of a healthy aquarium.
For everyone else, here’s a brief refresher on the nitrogen cycle in action:
What exactly is fish-in cycling? Fish-in cycling serves to jump-start the nitrogen cycle, an unseen three-step process where beneficial (good) bacteria establish themselves in your filter, protecting your fish from harmful ammonia.
For a more in-depth explanation of the nitrogen cycle, check out our detailed guide here. If you’re new to the hobby, it’s essential reading since a well-functioning nitrogen cycle is a critical component of a healthy aquarium.
For everyone else, here’s a brief refresher on the nitrogen cycle in action:
Important note: Nitrites and nitrates are easily confused since they differ by only one letter. Remember that nitrites are highly toxic to fish, while nitrates are not harmful in low concentrations.
There’s just one issue – A brand-new aquarium doesn’t contain any beneficial bacteria. Without them, toxic ammonia and nitrites accumulate, endangering your fish.
Thus, it’s your responsibility to initiate the nitrogen cycle. To accomplish this, you’ll need assistance from your fish – or, more specifically, their waste. As waste breaks down, it releases ammonia, stimulating the growth of beneficial bacteria. You might be wondering about a potential issue here:
If ammonia is harmful to fish and their waste is the ammonia source, won’t this harm them?
Well, that’s precisely what leads us to our next point…
In emergency situations, a fish-in cycle might be your only option. If that’s the case, cycling with fish is an acceptable solution because not doing so could result in the death of your fish. However, if you have a choice, you should avoid cycling your aquarium with fish inside.
Why?
Simply put, fish-in cycling is extremely stressful for your fish. Many fish won’t survive the process, and those that do often become more susceptible to diseases and have shorter lifespans. You’d want to keep your pet fish alive and healthy for as long as possible, right? Well, a fish-in cycle is a terrible way to begin.
So, what makes a fish-in cycle so harmful to fish? During the cycling process, you’re waiting for beneficial bacteria to form a colony in your aquarium. Once established, they’ll consume ammonia and nitrites as quickly as they’re produced.
The problem is:
While you’re waiting for the bacteria to multiply, your fish are exposed to elevated levels of ammonia and nitrites. Even at low concentrations, these toxic substances can stress and severely irritate your fish. Additionally, a fish-in cycle requires meticulous planning and leaves little room for mistakes. It’s not exactly beginner-friendly.
Now, it’s not that fish-in cycling doesn’t work—it definitely can. However, considering the potential harm it can cause your fish, it should be reserved for emergencies only. Given the availability of fishless cycling, it’s surprising to see the outdated fish-in cycle still being recommended.
So, why do people continue to advise cycling an aquarium with fish in it? During a conversation with a big-box pet store employee, I found out he was promoting the benefits of fish-in cycling. Interestingly, he was also trying to convince me to buy fish for my new aquarium. The reason was apparent—an extra sale. Quite an unethical tactic, right?
In other cases, though, the recommendation to cycle with fish is less malicious. Fish-in cycling is how our grandparents would have prepared their tanks. This method has been in use for quite some time; in fact, it was the only way to cycle an aquarium back then.
In these instances, people who suggest a fish-in cycle have the best intentions—they’re simply passing on what they learned years ago. While you can’t fault them for that, you can fault them for not keeping up with modern practices! Luckily, you’re now better informed!
I’m aware that some of you may disagree with me on this. Maybe you’ve successfully used a fish-in cycle numerous times without causing harm. That’s fine too! However, for beginners, a fishless cycle is undeniably the better option. In this context, a fish-in cycle should only be used when absolutely necessary.
I’ll let you in on a little secret:
You can predict the success or failure of your fish-in cycle before you even start.
No, really.
It all boils down to the number of fish you have in your aquarium.
More fish = more waste
As this waste breaks down into ammonia, your ammonia levels will increase rapidly. The quicker your ammonia levels rise, the greater the harm inflicted on your fish. So, what’s the ideal number of fish for a fish-in cycle?
The larger your aquarium, the more fish you can include in a fish-in cycle. Rule of thumb: One fish for every 10 gallons of water. So, if your tank is 1 gallon, only 1 fish. If your tank is 58 gallons, 5 fish.
Unsure about your tank size? Use AquaManLife.com’s volume calculator.
But what if you have more fish than your tank should hold Ideally, you’ll want to do one of the following:
Give your fish away – Return your fish, gift them to a friend, or contact your local fish club to see if anyone will take them.
Purchase a larger tank – A bigger tank will allow you to cycle with more fish.
But what if neither of these options is feasible? Well, sadly, it’s time for you to make a tough decision. Do you attempt to cycle your aquarium with all your fish inside and risk killing them all?
First off, the 2 most important items I can suggest you to have to perform this, is a water test kit such as this API one, and a water conditioner. The test kit is for obvious reasons and the water conditioner is to make the make your tap water safe to use for the fish. Tap water contains chloramine and chlorine – two chemicals. Not only are these chemicals toxic to fish, but they also kill that beneficial bacteria, which without that, your tank won’t cycle.
Before I proceed, I want to emphasize one thing:
Your fish’s lives are at risk!
It’s crucial that you carefully follow this guide. Read each step twice if necessary. Ensure you fully understand what you’re doing before moving forward. I can’t guarantee that your fish will survive the cycling process – some are more sensitive than others. However, by following this guide, you provide them with the best possible chance.
When it comes to fish-in cycling, you have two options – cycling with Seachem Prime or with water changes.
Note: This fish-in cycling method still requires a bottle of Seachem Prime or another water conditioner to dechlorinate your tap water. It’s also useful to have on hand in case of emergencies – should anything go wrong.
Step 1: Set up your aquarium
It’s time to set up your aquarium, including all the equipment – heaters, filters, air pumps, and more! Don’t forget to rinse everything with fresh water first!
Beneficial bacteria need a surface to cling to, like your substrate and filter media. By setting everything up, you provide as many surfaces as possible for bacteria to attach to.
Fill your tank with water, and remember to dechlorinate it with your water conditioner. Keep all electrical equipment, such as heaters, filters, and bubblers, turned on throughout the entire cycling process. This will not only keep your fish comfortable but also help your tank cycle faster.
Looking to cycle your tank quickly? Check out AquaManLife’s “Accelerate Your Aquarium Cycle: Proven Tips for Rapid Fish Tank Cycling Success“.
Step 2: Adding your fish
Before introducing your fish, acclimate them first. This will maximize their chances of survival. Feed your fish throughout the cycling process, but don’t overfeed them. More food leads to more waste, which in turn raises ammonia levels. Remove any uneaten food from the tank using a good aquarium net.
If a fish dies during the cycle, remove it immediately. Its decaying body will also produce ammonia. One fish death doesn’t necessarily mean all your fish will suffer the same fate – some might be more sensitive.
Step 3: Test, test, test, and test again
Use your ammonia test kit every 24 hours. Look for any sign of ammonia. It won’t be long before it appears.
Once your test kit shows positive for ammonia, proceed to the next step.
Step 4: Dealing with ammonia
When ammonia is detected, start dosing with Seachem Prime. Follow the instructions on the bottle to determine the proper dose for your tank size.
Seachem Prime is crucial in this method, as it binds ammonia, nitrite, and nitrate for 24 to 48 hours, making them harmless to your fish.
Keep dosing with Seachem Prime regularly to keep ammonia, nitrite, and nitrate under control.
When your test kit reads 2 ppm of ammonia, perform a 50% water change. This should reduce ammonia levels significantly.
Repeat this process until your ammonia levels stop rising quickly. Typically, this takes a week or two. When this occurs, move on to the next step.
Step 5: Nitrites start to appear
Now, test for nitrites. If none are present, continue repeating the previous step and testing for nitrites daily until you get a positive result.
With nitrite now in the mix, ensure you’re dosing with enough Prime to protect your fish from both ammonia and nitrites.
Simply add your nitrite and ammonia readings together to determine the required Prime dosage.
Keep repeating this process. Eventually, your ammonia levels will drop to zero, and you can proceed to the next step.
Step 6: Nitrates appear
Test for nitrates. If none are present, continue repeating the previous step and testing for nitrates daily until you get a positive result.
Once nitrates are detected, you’re almost done! Keep testing for ammonia, nitrites, and nitrates. Your ammonia levels should remain at zero, and your nitrite levels should be decreasing.
Continue dosing with Prime until both nitrite and ammonia levels reach zero. At this point, the beneficial bacteria are consuming them as quickly as they’re produced.
Congratulations! You’ve successfully completed a fish-in cycle.
Time to set up your aquarium, including all the equipment – heaters, filters, air pumps, and more! Rinse everything with fresh water first!
Beneficial bacteria need surfaces to cling to, like your substrate and filter media. By setting everything up, you provide as many surfaces as possible for bacteria to attach to.
Fill the tank with water, and remember to dechlorinate it with your water conditioner.
Keep all electrical equipment, such as heaters, filters, and bubblers, turned on throughout the entire cycling process. This will keep your fish comfortable and help your tank cycle faster.
Before adding your fish, acclimate them first to increase their chances of survival.
Feed your fish throughout the cycling process, but avoid overfeeding. More food leads to more waste, which raises ammonia levels. Remove any uneaten food from the tank.
If a fish dies during the cycle, remove it immediately. Its decaying body will produce ammonia. One fish death doesn't necessarily mean all your fish will suffer the same fate – some might be more sensitive.
Use your ammonia test kit every 24 hours.
Look for any sign of ammonia. It won't be long before it appears.
Once ammonia starts building up, test your aquarium twice a day, making it a routine.
Aim to keep ammonia levels low, at 0.25 parts per million (ppm) or less.
When ammonia levels reach 0.5 ppm, perform a 50% water change. This helps remove and dilute ammonia.
The frequency of water changes depends on your tank size and the number of fish you're cycling with.
Maintain this routine for at least a week before moving to the next step.
fter a week, you'll notice that ammonia levels aren't rising as quickly. Test for nitrites using your nitrite test kit. If positive for nitrites, you're in the first stage of the nitrogen cycle.
If no nitrites are detected, continue with Step 4 and keep testing for nitrites.
Nitrites are more toxic than ammonia. Keep nitrites as close to zero as possible by continuing water changes.
Monitor ammonia and nitrites daily, performing water changes when nitrite levels rise.
Keep doing this for at least another week before moving to the next step.
After another week, nitrite levels should stabilize. Test for nitrates using your nitrate test kit. If positive for nitrates, you're on the home stretch.
If nitrates aren't detected, continue with Step 5 and keep testing for nitrates. Patience is key.
Keep testing and monitoring your ammonia, nitrite, and nitrate levels.
If nitrate levels exceed 40 ppm, perform a water change. However, if you're conducting water changes to manage nitrites, nitrate levels might not reach that high.
Continue this process until both ammonia and nitrite levels read zero on the same day. Remember, the entire cycling process can take months, so be patient.
Hooray!
You’ve made it!
The beneficial bacteria in your tank are now abundant enough to consume ammonia and nitrites as quickly as they’re produced.
It may have taken some time, but trust me, it was worth it!
Your tank is now safe for your fish. Any fish that survived deserve a medal of honor, as they made the tank safe for any new fish you want to add.
On that note…
If you want to add more fish to your tank (assuming your tank is large enough), wait a week before adding up to three. This allows the bacteria to adjust to the increase in waste and grow in numbers to handle it.
Want to add even more fish? Wait another week and repeat.
Keep in mind that from now on, nitrates will continuously accumulate in your aquarium. Regular water changes are essential for maintaining low nitrate levels.
Phew, you did it. I knew you could!
By cycling your aquarium, you provide your fish with the best chance of living a happy and healthy life. The nitrogen cycle will run continuously in the background once it has started.
However, you’re not entirely out of the woods yet…
Regularly monitoring your ammonia and nitrite levels is still crucial to ensuring that nothing goes awry. Make testing your tank a part of your routine water change schedule.
Fish-in cycling is the process of establishing beneficial bacteria in a new aquarium with fish already present, allowing the nitrogen cycle to stabilize the tank’s environment.
The duration of fish-in cycling can vary from a few weeks to a couple of months, depending on factors like tank size, fish species, and the techniques used.
While fish-in cycling can be stressful for fish, following a proper guide and taking immediate measures can minimize risks and ensure a safe environment for your aquatic pets.
Cycling your aquarium and using a good quality filter media and plants can encourage the growth of beneficial bacteria.
You should consider testing your water regularly, especially during the initial cycling period. After that, aim to test every 2-4 weeks.
It’s best to wait until the cycling process is complete before adding more fish. Once the ammonia and nitrite levels reach zero, you can gradually introduce new fish, allowing the bacteria to adapt.
A successful fish-in cycle is achieved when ammonia and nitrite levels consistently read zero, indicating the presence of enough beneficial bacteria to handle the waste produced by your fish.
Water changes help maintain low ammonia and nitrite levels, keeping the environment safe for your fish and promoting the growth of beneficial bacteria.
Ideally, nitrate levels should be below 20 ppm, but the optimal level depends on the specific species of fish and plants in your tank.
If your fish exhibit stress during fish-in cycling, it’s crucial to perform immediate water changes, closely monitor water parameters, and provide a stress-free environment by maintaining proper tank conditions.
Perform an immediate water change, test your water quality, and assess the potential causes, such as overfeeding, a dead fish, or a malfunctioning filter. You can always contact us right away and we are happy to offer some advice. Or pop over to our community page where you can interact with other like minded aquarists!
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