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Does depleted KH stop the nitrogen cycle?

Soilwork

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I know in recent years theres has been a discussion about Ammonia Oxidising Archaea and their prevalence and tolerance in low pH waters. This was previously thought to stall the Ammonia Oxidising Bacteria. My question is are these Archaea dependent on KH?

Wastewater treatment facilities indicate that 7ppm alkalinity is used up per 1ppm ammonia nitrified. Does this present an issue in a KH depleted aquarium, theoretically speaking?
 
I know in recent years theres has been a discussion about Ammonia Oxidising Archaea and their prevalence and tolerance in low pH waters. This was previously thought to stall the Ammonia Oxidising Bacteria. My question is are these Archaea dependent on KH?

Wastewater treatment facilities indicate that 7ppm alkalinity is used up per 1ppm ammonia nitrified. Does this present an issue in a KH depleted aquarium, theoretically speaking?

Hi @Soilwork, I do not know the answer to your question, but I doubt it, given how many skilled hobbyists around run their planted (and stocked) tanks successfully at zero or close to zero KH - I would like to hear what the experts have to say though. I always felt it was sort of unnatural with a hard zero KH. When you look at natural tropical soft waterways there always seems to be some CO3 present. For the same reason I keep my own tanks at ~0.5 KH.

Cheers,
Michael
 
Hi @Soilwork, I do not know the answer to your question, but I doubt it, given how many skilled hobbyists around run their planted (and stocked) tanks successfully at zero or close to zero KH - I would like to hear what the experts have to say though. I always felt it was sort of unnatural with a hard zero KH. When you look at natural tropical soft waterways there always seems to be some CO3 present. For the same reason I keep my own tanks at ~0.5 KH.

Cheers,
Michael
Same here.
 
Hi all,
There is a thread that maybe of interest? and that has a lot more references in it <"The nitrifying microbes in aquariums and cycling">
I know in recent years theres has been a discussion about Ammonia Oxidising Archaea and their prevalence and tolerance in low pH waters. This was previously thought to stall the Ammonia Oxidising Bacteria. My question is are these Archaea dependent on KH?
I don't think that Ammonia Oxidising Archaea (AOA) are as dependent (as AOB) on high levels of dissolved oxygen or carbonate hardness <"Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels - The ISME Journal">1.

The reason for thinking this is partially just that they are found in much more acidic and oxygen depleted environments than AOB, but there are some papers beginning to appear that add the "how" to the "why" (from <"Unexpected Complexity of the Ammonia Monooxygenase in Archaea">)2.
............Ammonia-oxidizing archaea use the most energy-efficient aerobic pathway for CO2 fixation..
The form of TAN available is also dependent on pH, with ammonium NH4+ being the largest proportion at lower pH levels, which may also effect the microbial flora. <"Ammonia-oxidizing archaea have more important role than ammonia-oxidizing bacteria in ammonia oxidation of strongly acidic soils - The ISME Journal">3..

The AOB also actually use CO2 (via the same ammonia monooxygenase gene ), but have carbonate (CO3--) / bicarbonate (HCO3-) as their starting carbon source to provide the CO2. I think <"AOA can use CO2"> directly (from <"Ammonia-oxidizing archaea and complete ammonia-oxidizing Nitrospira in water treatment systems">)4.
..... All cultivated AOA are thus far considered chemolithoautotrophs because they gain energy from ammonia oxidation and fix carbon dioxide into biomass
and from <"https://www.pnas.org/doi/full/10.1073/pnas.1010981108">5
.....These findings strongly suggest that ammonia-oxidizing archaeal groups in soil autotrophically fix CO2 using the 3-hydroxypropionate–4-hydroxybutyrate cycle, one of the two pathways recently identified for CO2 fixation in Crenarchaeota. Catalyzed reporter deposition (CARD)-FISH targeting the gene encoding subunit A of ammonia monooxygenase (amoA) mRNA and 16S rRNA of archaea also revealed ammonia-oxidizing archaea to be numerically relevant among the archaea in this soil. Our results demonstrate a diverse and dynamic contribution of ammonia-oxidizing archaea in soil to nitrification and CO2 assimilation......
Wastewater treatment facilities indicate that 7ppm alkalinity is used up per 1ppm ammonia nitrified. Does this present an issue in a KH depleted aquarium, theoretically speaking?
No, I'm pretty sure it doesn't, the <"microbial flora in Aquarium filters"> will be very different from the one found in waste water treatment amd will be centred on a core of AOA and COMAMMOX Nitrospira. This is discussed in <"Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira">6..

I'll see what I can find for COMAMMOX Nitrospira and their carbon requirements.

cheers Darrel

1. Klotz, F., Kitzinger, K., Ngugi, D.K. et al. (2022) "Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels." ISME J 16, 1647–1656 . Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels - The ISME Journal.
2. Logan H. Hodgskiss, Michael Melcher, Melina Kerou, Weiqiang Chen, Rafael I. Ponce-Toledo, Savvas N. Savvides, Stefanie Wienkoop, Markus Hartl, Christa Schleper (2023) "Unexpected Complexity of the Ammonia Monooxygenase in Archaea" bioRxiv 2022.04.06.487334; doi: Unexpected Complexity of the Ammonia Monooxygenase in Archaea
3. Zhang, LM., Hu, HW., Shen, JP. et al. (2011) "Ammonia-oxidizing archaea have more important role than ammonia-oxidizing bacteria in ammonia oxidation of strongly acidic soils". ISME J 6, 1032–1045 (2012). https://doi.org/10.1038/ismej.2011.168
4. Sarah Al-Ajeel, Emilie Spasov, Laura A. Sauder, Michelle M. McKnight, Josh D. Neufeld, (2022) "Ammonia-oxidizing archaea and complete ammonia-oxidizing Nitrospira in water treatment systems," Water Research X, 15, Redirecting
5. Pratscher, J., Dumont, Marc and Conrad, R. (2011) Ammonia oxidation coupled to CO2 fixation by archaea and bacteria in an agricultural soil. Proceedings of the National Academy of Sciences, 108 (10), 4170-4175.
6. Bartelme RP, McLellan SL, Newton RJ. (2017) "Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira". Front Microbiol. Jan 30;8:101.
 
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Hi all,
There is a thread that maybe of interest? and that has a lot more references in it <"The nitrifying microbes in aquariums and cycling">

I don't think that Ammonia Oxidising Archaea (AOA) are as dependent (as AOB) on high levels of dissolved oxygen or carbonate hardness <"Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels - The ISME Journal">1.

The reason for thinking this is partially just that they are found in much more acidic and oxygen depleted environments than AOB, but there are some papers beginning to appear that add the "how" to the "why" (from <"Unexpected Complexity of the Ammonia Monooxygenase in Archaea">)2.

The form of TAN available is also dependent on pH, with ammonium NH4+ being the largest proportion at lower pH levels, which may also effect the microbial flora. <"Ammonia-oxidizing archaea have more important role than ammonia-oxidizing bacteria in ammonia oxidation of strongly acidic soils - The ISME Journal">3..

The AOB also actually use CO2 (via the same ammonia monooxygenase gene ), but have carbonate (CO3--) / bicarbonate (HCO3-) as their starting carbon source to provide the CO2. I think <"AOA can use CO2"> directly (from <"Ammonia-oxidizing archaea and complete ammonia-oxidizing Nitrospira in water treatment systems">)4.

and from <"https://www.pnas.org/doi/full/10.1073/pnas.1010981108">5


No, I'm pretty sure it doesn't, the <"microbial flora in Aquarium filters"> will be very different from the one found in waste water treatment amd will be centred on a core of AOA and COMAMMOX Nitrospira. This is discussed in <"Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira">6..

I'll see what I can find for COMAMMOX Nitrospira and their carbon requirements.

cheers Darrel

1. Klotz, F., Kitzinger, K., Ngugi, D.K. et al. (2022) "Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels." ISME J 16, 1647–1656 . Quantification of archaea-driven freshwater nitrification from single cell to ecosystem levels - The ISME Journal.
2. Logan H. Hodgskiss, Michael Melcher, Melina Kerou, Weiqiang Chen, Rafael I. Ponce-Toledo, Savvas N. Savvides, Stefanie Wienkoop, Markus Hartl, Christa Schleper (2023) "Unexpected Complexity of the Ammonia Monooxygenase in Archaea" bioRxiv 2022.04.06.487334; doi: Unexpected Complexity of the Ammonia Monooxygenase in Archaea
3. Zhang, LM., Hu, HW., Shen, JP. et al. (2011) "Ammonia-oxidizing archaea have more important role than ammonia-oxidizing bacteria in ammonia oxidation of strongly acidic soils". ISME J 6, 1032–1045 (2012). https://doi.org/10.1038/ismej.2011.168
4. Sarah Al-Ajeel, Emilie Spasov, Laura A. Sauder, Michelle M. McKnight, Josh D. Neufeld, (2022) "Ammonia-oxidizing archaea and complete ammonia-oxidizing Nitrospira in water treatment systems," Water Research X, 15, Redirecting
5. Pratscher, J., Dumont, Marc and Conrad, R. (2011) Ammonia oxidation coupled to CO2 fixation by archaea and bacteria in an agricultural soil. Proceedings of the National Academy of Sciences, 108 (10), 4170-4175.
6. Bartelme RP, McLellan SL, Newton RJ. (2017) "Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira". Front Microbiol. Jan 30;8:101.
Cheers Darrel.

This is absolutely fantastic stuff.

Regards
 
Hi all,
I'll see what I can find for COMAMMOX Nitrospira and their carbon requirements.
So far only the bits in <"Microbial community analysis of biofilters reveals a dominance of either comammox Nitrospira or archaea as ammonia oxidizers in freshwater aquaria">*.

They are two of the authors mentioned <"earlier in the thread">. It is an interesting paper. I've abstracted some sections from it.
....... 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......
....Among nitrifiers, comammox Nitrospira amoA genes were detected in all 38 freshwater aquarium biofilter samples and were the most abundant ammonia oxidizer in 30 of these samples, with the remaining biofilters dominated by AOA, based on amoA gene abundances...
........Approximately half of the sampled aquaria contained live plants. The average number of fish across all aquaria was ∼22, ranging from 0-150. Several aquaria were populated with cichlids, algae eaters (e.g., “Plecos”), or guppies, and many contained mixed tropical or marine fish; one aquarium housed a turtle. Aquarium ages averaged 3 years, ranging from 1 month to 13 years, and were subject to diverse maintenance regiments ......
....... 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 .....
....... Our reassessment of the ammonia oxidizing microorganisms in aquarium biofilters revealed an unexpected abundance of comammox Nitrospira in freshwater aquarium biofilters, which revises a previous description of aquarium nitrification that focused on AOA. Both qPCR and 16S rRNA gene sequencing data showed that comammox Nitrospira and AOA together dominate as ammonia oxidizers in freshwater aquarium biofilters .....
...... Overall, the ubiquitous presence of comammox Nitrospira within freshwater aquarium biofilters is consistent with their presence in similar environments, such as recirculating aquaculture system (RAS) biofilters, groundwater-fed biofilters, and aquaponics systems . Relatively low ammonia concentrations and high surface area for biofilm growth within biofilters are ideal conditions for microorganisms with slow growth rates and high yields, as originally predicted for comammox Nitrospira .....
Niche differentiation of ammonia oxidizers in aquarium biofilters
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. Our results do support the observations from previous studies that comammox Nitrospira and AOA are dominant in lower ammonia conditions.........
...... 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.
* Michelle M. McKnight, Josh D. Neufeld (2021) "Microbial community analysis of biofilters reveals a dominance of either comammox Nitrospira or archaea as ammonia oxidizers in freshwater aquaria".

cheers Darrel
 
Hi all,
Does this present an issue in a KH depleted aquarium, theoretically speaking?
Probably the bit that will be of most interest to you are tables S2 and S1 from <"Microbial community analysis of biofilters reveals a dominance of either comammox Nitrospira or archaea as ammonia oxidizers in freshwater aquaria">.
....... Participants also provided aquarium information including temperature, maintenance history, water source, and the number and species of fish and plants (Table S1-S2). ...Measured concentrations of total ammonia in sampled aquaria were relatively low, with an average concentration of ∼59 μg/L NH3-N. Nitrite was usually undetected, or low in most aquaria, with only three aquaria with elevated levels of >1 mg/L NO2--N (Table S2). In contrast, nitrate concentrations in most aquaria were relatively high (>1 mg/L NO3--N)......
McKnight_NeufeldTableS2.png


So mainly fairly hard (alkaline) water with high pH, dGH and dKH.

McKnight_NeufeldTableS1.png


Tank F33 looks quite interesting, ~RO water, plants and just a pair of Microctenopoma. The filter microbes were ~all COMAMMOX Nitrospira

F4.large.jpg

....... The genera associated with ammonia or nitrite oxidizing microorganisms present in the aquarium biofilter samples identified from the 16S rRNA gene sequences are illustrated by the bubble plot (top) with the size and number for each bubble representing the RA of each genus in each sample. Colours of bars and bubbles represent the respective groups of ammonia oxidizers, nitrite oxidizers, or comammox.

cheers Darrel
 
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Hi all,
I would have thought that AOA and AOB would both be dependent on KH as a source of carbon.
They definitely need an inorganic carbon source, and then it would be back to the <"form of TIC"> and whether the AOA, AOB and/or COMAMMOX Nitrospira can use CO2 / H2CO3 directly, or only indirectly, from the CO3-- or 2HCO3- component of the TIC. There is also oxygen availability to take into account <"Predominance of comammox bacteria among ammonia oxidizers under low dissolved oxygen condition">
Wastewater treatment facilities indicate that 7ppm alkalinity is used up per 1ppm ammonia nitrified.
We know that the <"canonical ammonia oxidising bacteria">, that perform nitrification in sewage sludge etc., need high dKH (so TIC as CO3-- or 2HCO3-) before they can utilise it. I don't know exactly how this relates to ammonia concentration, it may be that dKH is actually <"analogous to oxygen">, basically you only need a lot of it (<"and of oxygen">), because you have a lot of ammonia, and as that ammonia bioload diminishes so does the requirement for dKH.

1659562485440-png.191965


Using your @jaypeecee 's very useful graph we can see that the form of the TIC is pH dependent and we know that pH is, almost always, dependent on the amount of dKH. We also know that COMAMMOX Nitrospira and / or AOA are occurring in both alkaline and acidic conditions (in aquarium filters etc.) and from this we can deduce that they must be able to utilise the CO2, because there isn't any 2HCO3- or CO3-- present, if that makes sense?

I'm now wondering if the same actually applies to AOB, all that is different is the amount of ammonia. All the Ammonia Oxidising Organisms (AOO) have the ammonia monooxygenase gene <"Ammonia oxidation: Ecology, physiology, biochemistry and why they must all come together">, possibly when you have a lot of ammonia there isn't enough CO2 present and, at that point, some organisms (AOB) can convert the reserve of TIC (the carbonate buffer) into "extra" CO2? I'll see what I can find.

cheers Darrel
 
Hi all,
I'll see what I can find.
It looks like <"Ammonia oxidation: Ecology, physiology, biochemistry and why they must all come together">* may have all the answers, but I would need to talk to a microbial biochemist to really be able to interpret what she says.
........The bioavailable ammonia concentration and environmental pH are connected: ammonia exists in two different forms in the environment, non-protonated ammonia (NH3) and its protonated form ammonium (NH4+) that are in a pH-dependent equilibrium (pKa = 9.27). In acidic conditions, the amount of available NH3 is extremely low. A 1974 study by Suzuki and colleagues demonstrated that the AOB N. europaea is only able to use ammonia, rather than ammonium, which has long been considered the key reason why AOB are unable to grow in acidic environments (Suzuki, Dular and Kwok 1974). This study is still the cornerstone of ammonia oxidation research although it has not been repeated with other strains of AOB, AOA nor comammox Nitrospira. However, the inability to use ammonia in low pH does not exclude survival and activity of AOB in these conditions: AOB are able to grow in acidic conditions using urea as substrate and by growing in biofilms and aggregates (de Boer et al.1991; Burton and Prosser 2001). The notion that ammonia oxidation is problematic at low pH was overturned by the discovery of the first obligately acidophilic ammonia oxidiser, N. devanaterra (Lehtovirta-Morley et al.2011). Originally isolated from an acidic agricultural soil, this archaeon grows autotrophically in the pH range of 4–5.5 in laboratory culture with ammonium chloride as its sole energy source. Although Nitrosotalea is the only obligately acidophilic ammonia oxidiser described to date, it is unlikely to be the only microorganism performing nitrification in acidic soils. Cultivation of acid-tolerant γ- and β-proteobacterial AOB has been reported (de Boer et al.1991; Hayatsu et al.2017). In addition to AOB that tolerate acidic conditions and are found in acidic soils, the archaeal genus Nitrososphaera is abundant in many acidic soils globally and has been reported to grow in acidic soil microcosms (Gubry-Rangin et al.2011; Wang et al.2014).....
I think this is the bit that answers @jaypeecee's <"question">.
....... Both AOB and comammox Nitrospira fix atmospheric CO2, AOB by the Calvin cycle and the comammox Nitrospira by reductive tricarboxylic acid cycle, whereas AOA fix HCO3− by the hydroxypropionate–hydroxybutyrate cycle (Berg et al.2007). Energetic requirements of these pathways are different and the thaumarchaeal hydroxypropionate–hydroxybutyrate cycle is the single most efficient aerobic inorganic carbon assimilation pathway known (K"o"onneke et al.2014). In addition, CO2 and HCO3− are in a pH-dependent equilibrium and the concentration of HCO3− decreases with a decreasing pH. This is rather paradoxical given the existence of acidophilic AOA, and potentially implies that acidophilic AOA have a very high affinity for HCO3− in order to grow at low pH. The ecological and physiological consequences of these differences are largely unexplored.........
I also think it implies that
..... possibly when you have a lot of ammonia there isn't enough CO2 present and, at that point, some organisms (AOB) can convert the reserve of TIC (the carbonate buffer) into "extra" CO2?
may be right.
* Lehtovirta-Morley, Laura E (2018) "Ammonia oxidation: Ecology, physiology, biochemistry and why they must all come together"> FEMS Microbiology Letters 365

cheers Darrel
 
Thanks Darrel.

So the take home so far is that AOA and COMM nitro can occur in a wide range of pH levels. The only tank (we can see) that used RO is the only one that has a relatively low kH so all tanks in the table had some KH. This means we cannot say for certain that KH is NOT fundamental for AOA to function.

I agree with your extrapolation regarding the pH and relation to KH suggesting that low pH waters must have low to zero KH and therefore be able to complete nitrification in KH depleted waters. Especially since now we understand AOA can utilise co2. This was my initial hypothesis and actually the question that brought me to post this thread.

Lastly that AOB are predominant in higher ammonia loadings but relatively small by comparison in low ammonia loadings.

I wonder if Dr Hanovecs early research was based on data from sewage treatment and was applied to make bottled bacteria based on this information.

Regards
 
Hi all,
This means we cannot say for certain that KH is NOT fundamental for AOA to function.
I think that is just an unknown, I'm still slogging my way through <"Ammonia oxidation: Ecology, physiology, biochemistry and why they must all come together">, but she says
....... In addition, CO2 and HCO3− are in a pH-dependent equilibrium and the concentration of HCO3− decreases with a decreasing pH. This is rather paradoxical given the existence of acidophilic AOA, and potentially implies that acidophilic AOA have a very high affinity for HCO3− in order to grow at low pH. The ecological and physiological consequences of these differences are largely unexplored.........
This wouldn't technically require any dKH, but would give you a cut-off point at about pH4, where all the TIC is in the form of CO2 and H2CO3.
I wonder if Dr Hanovecs early research was based on data from sewage treatment and was applied to make bottled bacteria based on this information.
It was. You would need to see what he says in <"Dr Timothy Hovanec's comments about Bacterial supplements">. I think he implies (in our thread) that the production method may have changed over time?

cheers Darrel
 
‘and potentially implies that acidophilic AOA have a very high affinity for HCO3− in order to grow at low pH’

Can you explain what she means by this?

When you say cut off point at what pH would the TIC by just co2?

Thanks
 
Hi all,
and potentially implies that acidophilic AOA have a very high affinity for HCO3− in order to grow at low pH...Can you explain what she means by this?
She is suggesting that the AOA and / or COMAMMOX Nitrospira are very effective at utilising any remaining HCO3- ions, although they form a very small proportion of the TIC.
at what pH would the TIC by just co2?
According to the chart ~pH 4.
1659562485440-png.191965


cheers Darrel
 
Hi Darrel further up (post 4) it says that AOA can fix co2 directly from the atmosphere and that AOB use co2 a
but require co3 and bicarbonate as a starting source to fix carbon.

Post #10 contradicts this by stating ....... Both AOB and comammox Nitrospira fix atmospheric CO2, AOB by the Calvin cycle and the comammox Nitrospira by reductive tricarboxylic acid cycle, whereas AOA fix HCO3− by the hydroxypropionate–hydroxybutyrate cycle

She has the AOA and AOB flipped?

My understanding is AOA can use co2 directly but AOB need to fix co3 and Hco3 in order to obtain their carbon source which is why AOB prevalent in wastewater treatment use up KH

Regards
 
Hi all,
Hi Darrel further up (post 4) it says that AOA can fix co2 directly from the atmosphere and that AOB use co2 a
but require co3 and bicarbonate as a starting source to fix carbon............. My understanding is AOA can use co2 directly but AOB need to fix co3 and Hco3 in order to obtain their carbon source which is why AOB prevalent in wastewater treatment use up KH
I'm still not sure, I don't have enough biochemical knowledge. I'd assumed that AOA must be able to use CO2, because there isn't any HCO3- present in acidic conditions, but the suggestion seems to be that they are just more efficient scavengers of the small proportion of HCO3- present.

cheers Darrel
 
Either way I think a lot of this data really does make fishless cycling pretty pointless.

For me personally, I think that I worry much less about ‘old tank syndrome’ based on this research given that average ammonia loadings are in the micrograms per litre with an abundance of plants and microbes able to oxidise ammonia without the presence of KH in acidic mediums.

Regards
 
Hi all,
Either way I think a lot of this data really does make fishless cycling pretty pointless.
That is my view as well.

It would only be in the <"Mbuna scenario"> that adding ammonia and <"a microbial supplement"> would have any validity. It isn't a route I'm ever going down, but if I was? I would use Tim Hovanec's <"one and only">.
I think that I worry much less about ‘old tank syndrome’ based on this research given that average ammonia loadings are in the micrograms per litre with an abundance of plants and microbes able to oxidise ammonia without the presence of KH in acidic mediums.
I'm pretty sure that none of us will ever see <"old tank syndrome"> again. When I started fish keeping I used to kill my fish with <"sickening regularity">, and unfortunately that was a common experience for many fish keepers.

I (and most other people) used gravel, had no or limited plant growth, didn't have a proper filter, never changed any water etc. and I now realise that any / all of these were contributory factors.

cheers Darrel
 
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Takes me back to my other thread about old tank syndrome


I suspect what people thought was responsible for fish deaths (pH dropping and lack of KH) was actually just poor practice all round (myself included). Like you say Darrel any combination of overstocking, overfeeding, poor filtration, no plants, no water changes. Having said that I’m more confident that OTS was always used to deter the no water change keepers. I’m more confident that if you have a decent amount of healthy plants, sensible stocking levels, feed responsibly, have good mature biofiltration and keep soft water species that going much longer between water changes won’t be an issue and I can happily continue changing water with rain and RO and not have to worry about the nitrogen cycle crashing.

Regards
 
Hi all,
I’m more confident that if you have a decent amount of healthy plants, sensible stocking levels, feed responsibly, have good mature biofiltration and keep soft water species that going much longer between water changes won’t be an issue and I can happily continue changing water with rain and RO and not have to worry about the nitrogen cycle crashing.
I'm pretty sure you are right. A lot of people will have run their tanks at low dKH values for extended time periods (I'm one of them) without any biofiltration issues. I like to <"change some water">, but that is partially because of <"the horrible things I have done in the past">.

cheers Darrel
 
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