Emergency fish in cycle
Posted: Fri Sep 05, 2025 3:46 pm
Emergency fish in cycle
Now we 100% don’t agree with knowingly cycling your tank with a fish in there. The reasons we don’t want this to be the case is that having unstable parameters will affect the fish. Unstable parameters are spikes in ammonia, nitrite and nitrate.
Cycling with a fish in there is exposing them to toxins that are harmful to them and will stress them out, they can get burns from the ammonia which look like red areas that are sore and raw, they can be gulping for air at the surface, their fins can become clamped and they stay listlessly at the bottom, their gills can bleed, they can become lethargic as they will be weak from poor water quality and betta especially can end up with torn fins which can develop into fin rot and or a bacterial infection and the worst outcome could be the fish getting dropsy which is organ failure and there is no cure for this. There is more information on these diseases and conditions in the guides section under diseases.
So because all these things can happen we need to make the environment safe for them.
This file on how to cycle with a fish is not so people can just go and do it but more so for those emergency situations where you’ve been given the wrong advice and you now currently have a fish in the tank and need to go with it now.
This method means it’s basically a lot of work on your part doing water changes to make it safe for them.
How to do it.
- So the first thing you need to get is a good liquid water testing kit such as API Master Kit which is my preference or NT Labs Multi Test Kit. The reason you need this is because you simply won’t know what’s going on without it. This will let you know exactly how much ammonia, nitrite or nitrate is in the tank. Because they are toxic to fish you need to remove them.
- Prime water conditioner by seachem is also your number one best friend. This conditioner although removes chlorine from tap water, it also binds ammonia and nitrite for 24 hours meaning that it makes the toxins less harmful to the fish for the duration in between the daily water changes.
How toxins build up
- When fish are in the tank their uneaten food and pee and poop produces ammonia. Ammonia is toxic to them. Dead plants can also produce ammonia but we’ll focus mainly on fish waste. So because uneaten food produces ammonia we want to minimise the amount of waste that’s in there so that it doesn’t spike too high. It’s best individually adding each pellet or worm and only adding more once eaten.
What is the cycling process
- There are 3 stages to the cycling process which is ammonia, nitrite and nitrate.
- The first stage is ammonia and our source for this is basically the fishes waste, so when we test our water we will expect to see this appear at a certain level. For photo purposes I’ll include just API tests to indicate what I mean, they have a colour indicator chart to show your levels.
- So when you test your water daily we are looking at the colour of the test, we don’t want to have high ammonia or nitrite in there because it will poison your fish. If there is a reading of any of these then you need to water change to manually remove the toxins and dose prime because this binds ammonia and nitrite for 24 hours if there is any remaining.
- This can seem like a long road and it may mean that you are daily water changing from 50-80% and sometimes back to back water changing for a while but it’s a necessary step. Betta do have a low bioload so you may end up being lucky and only having to do changes every couple of days.
- This all depends on what your water test says, so you need to be testing daily.
- What happens when there is ammonia in the tank is we are basically growing bacteria that can eat the ammonia, it does take time for this to happen so be patient. After a period of time as the bacteria is growing more you will start to see that the levels will start dropping. The bacteria doesn’t remove the ammonia it changes it into nitrite which is the next step in the cycling process.
- At this stage you will start to see your water tests for nitrite start to increase and this is your indicator that it’s progressing. You just keep testing daily at this point. You will then start to see the nitrite levels dropping. As it’s dropping this shows that another type of bacteria is growing to eat this up, and again this doesn’t remove it, it just converts it into nitrate which is the final stage in the cycling process.
- What we are looking for is you testing the water and getting zero readings on ammonia and nitrite and some readings for nitrates.
- Nitrates being the last step to the cycle indicates that it’s ready.
- Ammonia and nitrite need bacteria to establish to cope with these toxins as they are very toxic to fish. Nitrates are the part where it’s us that remove them. Plants also play a factor in this too but we’ll keep it simple and relate lowering these to us changing water.
- Nitrates are tolerable at levels from 5-10ppm, you can get slightly higher in a planted tank but it’s easier to go with the lower the better, but it’s not always possible to stay within that bracket as some tap water contains higher than this level so it’s unrealistic to expect the tank to be within that range when the tap is higher.
Now that I’ve explained it in a little detail I’ll recap simply what’s happening.
- Your fish creates ammonia.
- Bacteria grows and eats the ammonia and changes it into nitrite.
- Another bacteria grows and eats the nitrite and changes it into nitrate.
- You want 0 readings on ammonia and nitrite and some readings on nitrate indicating that the tank is fully cycled.
Now that the tank is cycled you should still water test initially a couple of times a week to make sure everything remains stable and then you can scale it back to once a week.
I’ve added a photo of the prime dosage. Because it’s super concentrated you need very little and some smaller tanks from 20L is harder to dose in ml so it’s easier to dose in drops. Not all prime bottles have a dropper so if you have one without you can decant some into a dropper bottle, I used to use my hayfever eye drop bottle, or a pipette or what I do now is I poke a tiny hole into the foil seal and that effectively turns the bottle into a dropper.
Now we 100% don’t agree with knowingly cycling your tank with a fish in there. The reasons we don’t want this to be the case is that having unstable parameters will affect the fish. Unstable parameters are spikes in ammonia, nitrite and nitrate.
Cycling with a fish in there is exposing them to toxins that are harmful to them and will stress them out, they can get burns from the ammonia which look like red areas that are sore and raw, they can be gulping for air at the surface, their fins can become clamped and they stay listlessly at the bottom, their gills can bleed, they can become lethargic as they will be weak from poor water quality and betta especially can end up with torn fins which can develop into fin rot and or a bacterial infection and the worst outcome could be the fish getting dropsy which is organ failure and there is no cure for this. There is more information on these diseases and conditions in the guides section under diseases.
So because all these things can happen we need to make the environment safe for them.
This file on how to cycle with a fish is not so people can just go and do it but more so for those emergency situations where you’ve been given the wrong advice and you now currently have a fish in the tank and need to go with it now.
This method means it’s basically a lot of work on your part doing water changes to make it safe for them.
How to do it.- So the first thing you need to get is a good liquid water testing kit such as API Master Kit which is my preference or NT Labs Multi Test Kit. The reason you need this is because you simply won’t know what’s going on without it. This will let you know exactly how much ammonia, nitrite or nitrate is in the tank. Because they are toxic to fish you need to remove them.
- Prime water conditioner by seachem is also your number one best friend. This conditioner although removes chlorine from tap water, it also binds ammonia and nitrite for 24 hours meaning that it makes the toxins less harmful to the fish for the duration in between the daily water changes.
How toxins build up- When fish are in the tank their uneaten food and pee and poop produces ammonia. Ammonia is toxic to them. Dead plants can also produce ammonia but we’ll focus mainly on fish waste. So because uneaten food produces ammonia we want to minimise the amount of waste that’s in there so that it doesn’t spike too high. It’s best individually adding each pellet or worm and only adding more once eaten.
What is the cycling process- There are 3 stages to the cycling process which is ammonia, nitrite and nitrate.
- The first stage is ammonia and our source for this is basically the fishes waste, so when we test our water we will expect to see this appear at a certain level. For photo purposes I’ll include just API tests to indicate what I mean, they have a colour indicator chart to show your levels.
- So when you test your water daily we are looking at the colour of the test, we don’t want to have high ammonia or nitrite in there because it will poison your fish. If there is a reading of any of these then you need to water change to manually remove the toxins and dose prime because this binds ammonia and nitrite for 24 hours if there is any remaining.
- This can seem like a long road and it may mean that you are daily water changing from 50-80% and sometimes back to back water changing for a while but it’s a necessary step. Betta do have a low bioload so you may end up being lucky and only having to do changes every couple of days.
- This all depends on what your water test says, so you need to be testing daily.
- What happens when there is ammonia in the tank is we are basically growing bacteria that can eat the ammonia, it does take time for this to happen so be patient. After a period of time as the bacteria is growing more you will start to see that the levels will start dropping. The bacteria doesn’t remove the ammonia it changes it into nitrite which is the next step in the cycling process.
- At this stage you will start to see your water tests for nitrite start to increase and this is your indicator that it’s progressing. You just keep testing daily at this point. You will then start to see the nitrite levels dropping. As it’s dropping this shows that another type of bacteria is growing to eat this up, and again this doesn’t remove it, it just converts it into nitrate which is the final stage in the cycling process.
- What we are looking for is you testing the water and getting zero readings on ammonia and nitrite and some readings for nitrates.
- Nitrates being the last step to the cycle indicates that it’s ready.
- Ammonia and nitrite need bacteria to establish to cope with these toxins as they are very toxic to fish. Nitrates are the part where it’s us that remove them. Plants also play a factor in this too but we’ll keep it simple and relate lowering these to us changing water.
- Nitrates are tolerable at levels from 5-10ppm, you can get slightly higher in a planted tank but it’s easier to go with the lower the better, but it’s not always possible to stay within that bracket as some tap water contains higher than this level so it’s unrealistic to expect the tank to be within that range when the tap is higher.
Now that I’ve explained it in a little detail I’ll recap simply what’s happening.- Your fish creates ammonia.
- Bacteria grows and eats the ammonia and changes it into nitrite.
- Another bacteria grows and eats the nitrite and changes it into nitrate.
- You want 0 readings on ammonia and nitrite and some readings on nitrate indicating that the tank is fully cycled.
Now that the tank is cycled you should still water test initially a couple of times a week to make sure everything remains stable and then you can scale it back to once a week.
I’ve added a photo of the prime dosage. Because it’s super concentrated you need very little and some smaller tanks from 20L is harder to dose in ml so it’s easier to dose in drops. Not all prime bottles have a dropper so if you have one without you can decant some into a dropper bottle, I used to use my hayfever eye drop bottle, or a pipette or what I do now is I poke a tiny hole into the foil seal and that effectively turns the bottle into a dropper.