Cycling Tanks

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Levi R.

Aquarium Advice Apprentice
Joined
Jan 8, 2023
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I know I will 100% get backlash for this, but has anyone else never cycled a tank? I understand the nitrogen cycle, but I have never ever cycled a tank in my life. When i was a beginner, i bought a 29 gallon and filled it up. I put some gravel and some rocks from my backyard, and then added a oscar, three african cichlids, and a pleco. I never had an issue. Of course, i eventually rehomed them, after 6 months. Ever since then, i have 6 tanks that i have put fish in the same day i set them up. I have never had a water spike, and i only do water changes on my 20 and my 29, and one of my 10s as they all have rams. Am i just lucky or does this happen to everyone?
 
A tank will cycle whether you actively engage with the process or not. Its just something that happens. All the various processes that we call cycling mean is that it will be safer for your fish than just letting it cycle on its own with no control of the process.

I cant really comment on whether you are lucky or not as there isnt much detail on what you did. Maybe your water is acidic, ammonia isnt really toxic in acidic water. Maybe those fish you rehomed lived with health issues, harm from ammonia is a long term thing. Maybe you have live plants and they took up ammonia quicker than is than it can make the water toxic. Maybe some other factor.

But your tanks did cycle.
 
A tank will cycle whether you actively engage with the process or not. Its just something that happens. All the various processes that we call cycling mean is that it will be safer for your fish than just letting it cycle on its own with no control of the process.

I cant really comment on whether you are lucky or not as there isnt much detail on what you did. Maybe your water is acidic, ammonia isnt really toxic in acidic water. Maybe those fish you rehomed lived with health issues, harm from ammonia is a long term thing. Maybe you have live plants and they took up ammonia quicker than is than it can make the water toxic. Maybe some other factor.

But your tanks did cycle.



Of course they cycled, i just meant i never waited for them to cycle. My water is pretty high PH, but is soft. I didn't have any live plants in with the cichlids, and i never had any ammonia issues. I honestly do not know what happened. I used a filter cartridge for a while, before switching to filter floss. Now with all my other tanks i use live plants and i add used filter media to all of my filters, but i am stumped by the first one i got.
 
It just means that the ammonia wasn’t able to build up to toxic levels. 29 gallons is a fairly large volume of water and I assume the fish were rather small when first added?

With higher ammonia loadings it is possible for the pH to drop because the microbes that prefer ammonia also consume carbonate hardness and once the carbonate hardness has been consumed the pH will fall. If your water is naturally soft this might not take long.

Probably a series of fortunate events that will definitely not apply in all scenarios.
 
Of course they cycled, i just meant i never waited for them to cycle. My water is pretty high PH, but is soft. I didn't have any live plants in with the cichlids, and i never had any ammonia issues. I honestly do not know what happened. I used a filter cartridge for a while, before switching to filter floss. Now with all my other tanks i use live plants and i add used filter media to all of my filters, but i am stumped by the first one i got.
So your question really is "does everyone cycle tanks before adding fish?"

No. Historically fish in cycles where the norm, and even now i would expect most aquariums are cycled using fish. People will generally get their advice from fish stores, and ive never heard a fish store advise a fishless cycle because they want to sell you fish ASAP.

Whether knowingly or not, you have been doing a fish in cycle. Stock lightly for the size of your tank, change water, and add in new fish gradually is the essence of fish in cycles. Do this and you will likely never see any elevated water parameters, and dont need to know anything about cycling.
 
So your question really is "does everyone cycle tanks before adding fish?"

No. Historically fish in cycles where the norm, and even now i would expect most aquariums are cycled using fish. People will generally get their advice from fish stores, and ive never heard a fish store advise a fishless cycle because they want to sell you fish ASAP.

Whether knowingly or not, you have been doing a fish in cycle. Stock lightly for the size of your tank, change water, and add in new fish gradually is the essence of fish in cycles. Do this and you will likely never see any elevated water parameters, and dont need to know anything about cycling.

Exactly that.(y) Fish in was the only way "back in the day." We didn't call it "cycling" but called it the " breaking in" or "establishing" of a tank.
To the OP's point " I put some gravel and some rocks from my backyard," that is where the nitrifying bacteria most likely got into the tank. In a new aquarium, which is similar to being in a sterile environment, we are waiting for nitrifying bacteria to develop. When you use items like used filter material from an established tank or sponge filter squeezings where that bacteria already exists, the whole process happens much more quickly.
It's my understanding that only tanks with a very low Ph don't go through the "cycling" period because the nitrifying bacteria can not live in that kind of environment so the ammonia produced does not convert and the fish survive because at the lower Ph scale, the ammonia is naturally converted from toxic ammonia to non toxic ammonium. Other than that, every tank goes through the nitrogen cycle whether you see it or not. Fish that are more fragile do not handle fish in cycling. The fish that the OP put into the tank first are not fragile fish so it's not surprising to me that they made it through that period.
 
A few other possibilities.

- If OP is saying they stocked a 6" oscar, 5" pleco, 3 x 3" undefined cichlids, tested every day, 0ppm ammonia, nitrite, or nitrate. We might then start with how they are testing and possible inaccuracies.

- If that didnt throw up any issues with the testing, then you might take a look at their filtration. They mention a filter cartridge. Many cartridges contain zeolite which we know absorbs ammonia. As long as the zeolite remains active you would see low to zero ammonia, nitrite and nitrate but your cycle wouldnt establish. Once the zeolite expires, if you didnt replace the cartridge in time, only then you would see ammonia and wonder what crashed your cycle.

- As point 1, but the nitrate steadily rises in those daily tests. It would then be a reasonable conclusion that the cycle established quickly.

So many variables about that could explain what OP is seeing.

As to low pH stalling cycles im not sure thats fully the case. Denitrifying bacteria needs KH, and low pH is a sign of low KH and i think thats where low pH stalls cycles comes from. Even with low KH in your source water, there is usually enough to cycle a tank as long as its regularly replenished through water changes. 7ppm KH needed to cycle out 1ppm ammonia into nitrate.
 
Hi All,

I’ve had this discussion regarding pH and stalling cycles here and elsewhere. I am more than happy to provide links to discussions and sample papers via pm if interested but the first thing we need to try and accept is that low pH doesn’t stall cycles. Low pH makes ammonia become ammonium.

There are organisms that prefer ammonia as a substrate and there are organisms that prefer ammonium.

In high ammonia environments such as wastewater the organisms are predominantly bacteria based and they use carbonates as part of the nitrification process.

If there are not enough carbonates the pH drops and the substrate becomes ammonium. In this type of environment the organisms are predominantly Archaea. This is a low ammonia environment and this is what the typical aquarium filter is.

Nitrifying Archaea have been shown to live in acidic mediums and can use co2 as a carbon source meaning that nitrification happily continues at low pH levels.

The previous data with regards to low pH stalling the cycle is from wastewater filters where KH is needed. Having said that the cycle is stalling only due to a transition. If we dose large amounts of ammonia like in a fishless cycle we are encouraging the organism that will not be our end organism to grow and we are depleting our KH reserves in the process. Thats why water changes kickstart the cycle process. This to me is pointless however, because the aquarium filter is going to change.

Fish in cycles SHOULD be encouraged. We should remove the fishless cycle from the sticky section and promote the correct method for fish in cycling. We would have far less cycling related problems this way and fish in cycling has many benefits.
 
Interesting thread...learned some things.


Fish in cycles SHOULD be encouraged. We should remove the fishless cycle from the sticky section and promote the correct method for fish in cycling. We would have far less cycling related problems this way and fish in cycling has many benefits.

Caliban--what are the benefits of a fish in cycle vs fishless?
 
Interesting thread...learned some things.









Caliban--what are the benefits of a fish in cycle vs fishless?


Well, if done correctly, you can begin stocking fish straight away so you’re not staring at an empty tank. There is less frustration because the KH won’t deplete and stall the cycle. Less reliance and initial investment in mostly inaccurate test kits. No need to buy and keep household ammonia and you are growing the correct microbial communities in the aquarium filter straight off the bat.
 
Well, if done correctly, you can begin stocking fish straight away so you’re not staring at an empty tank. There is less frustration because the KH won’t deplete and stall the cycle. Less reliance and initial investment in mostly inaccurate test kits. No need to buy and keep household ammonia and you are growing the correct microbial communities in the aquarium filter straight off the bat.

Interesting.
Didn't realize a fishless cycle could deplete KH...then again, I'd probably be monitoring it in a new tank anyway.

Tucking this all away for the future, in case I'd ever need to start from scratch in the future.
 
Nitrogen cycle depletes KH in general. About 7ppm KH is used up to cycle out 1ppm ammonia to nitrate.

In a fishless cycle you are dosing far higher amounts of ammonia than fish would produce in the same period of time, so KH is depleted far quicker in fishless cycle than you would expect in a tank full of fish.
 
Interesting.

Didn't realize a fishless cycle could deplete KH...then again, I'd probably be monitoring it in a new tank anyway.



Tucking this all away for the future, in case I'd ever need to start from scratch in the future.


A fishless cycle will but a regular running aquarium especially with plants will take an age to deplete KH and even then the cycle will continue because of the Archaea and COMAMMOX microbes
 
Andy Caliban and Aiken--
So, in sum, you could probably say a fishless cycle results in greater pH swings and would take longer to stabilize?

(These are all theoretical questions... just pondering what I would do if I needed to start from scratch or help someone through the process. )
 
I find interesting that in the paper the scientists refer to greater than 1ppm nitrate ‘relatively high’
 
Comammox Nitrospira amoA genes were detected across all 38 freshwater aquarium biofilter samples and were dominant ammonia oxidizers within 30 of the freshwater biofilters

Microbial profiles of freshwater biofilters revealed that community composition was correlated with temperature, aquarium size, and general hardness of the water. Other studies have demonstrated the importance of environmental, biological, and physical factors, such as temperature, filter support material, and fish species as being involved in differentiating biofilter microbial communities in systems like RAS, water treatment, and aquaponics

We observed that the majority of the aquarium biofilters were dominated by either AOA or comammox Nitrospira, although it is not clear what factors may be contributing to their distributions. Previously, pH and ammonia concentration were identified as two key factors governing the abundance of different ammonia oxidizing microorganisms in the environment (50). Our results do support the observations from previous studies that comammox Nitrospira and AOA are dominant in lower ammonia conditions. Previous work shows that both AOA and comammox Nitrospira compete favourably in low ammonia conditions, with several cultivated representatives having high affinities for ammonia including Nitrospira inopinata, Ca. N. kreftii, Nitrosopumilus maritimus, and Ca. Nitrosotenuis aquarius (38, 51, 52). However, at this time there are only have a few cultivated representatives of comammox Nitrospira where ammonia affinities have been measured. Additionally, there are several AOA species that are also known to have tolerance for higher ammonia concentrations, such as those from the genus Nitrosocosmicus (53). We noticed that there was a higher relative abundance of Nitrosotenuis spp. than Nitrosocosmicus spp. for freshwater samples.
Although most freshwater aquaria sampled were low in ammonia, there was one sampled aquarium (FW-F34) that had a high concentration of total ammonia and was dominated by AOB amoA genes. In all other freshwater samples, AOB fell below 14% RA, with most being < 1% of the total ammonia oxidizers detected with qPCR. The low abundance of both detected comammox Nitrospira and AOB is reflected in the overall microbial community of FW-F34 where associated genera of Nitrospira and Nitrosomonas are both present at a RA of > 0.5%. Although this sample suggests AOB might favour high ammonia concentrations over AOA and comammox, more data is needed to support this hypothesis. The effects of ammonia concentration on ammonia oxidizer abundance may be easier to test under experimental conditions with controlled ammonia concentrations as most aquaria naturally have low levels of ammonia with well-established nitrifying communities in their biofilms.

Overall, this work has further clarified our understanding of ammonia oxidation in aquarium biofilters revealing that comammox Nitrospira are ubiquitous in freshwater biofilters, and the dominant ammonia oxidizers are either comammox Nitrospira and AOA. Now that we hopefully have completed our picture of the autotrophic microbial members involved in aquarium ammonia oxidation, future research should work to further address the factors that may be involved in niche differentiation in these environments and explore the contributions from each group to ammonia oxidation in the biofilters. An improved understanding of this microbially mediated process in aquaria is important to improve and optimize current water treatment in the aquaculture industry and could potentially lead to the development of new and improved supplements for aquarium biofilters.

From the link above
 
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