Mythbusting Fishless Cycling For Beginners

I thought I’d create this thread as a resource for others who are wanting to attempt fishless cycling. I hope others find this information as useful as I did.

(1) Beneficial bacteria die in 24 hours if they’re not fed. MYTH!

Short answer: Beneficial bacteria don’t die in 24 hours if they’re not fed. You don’t need to dose ammonia daily.

Long answer: Bollmann, Schmidt, Saunders, and Nicolaisen (2005) indicates that after Nitrosospira briensis was “starv[ed] up to 10 days… within 10 min after the addition of fresh NH4+, 100% activity was regained.”

Likewise, Bollman, Bar-Gilissen and Laanbroek (2002) report that Nitrosomonas europaea “after 1-10 weeks of ammonium deprivation… became almost immediately active after the addition of fresh ammonium."

(2) 5 ppm ammonia will stall a cycle. MYTH!

Short answer: 5 ppm ammonia won’t stall a cycle. Very high concentrations (far more than is ever seen in household aquariums) are required to stall a cycle.

Long answer: Meiklejohn (1954) notes that “nitrite depressed both respiration and growth of Nitrosomonas… Nitrobacter was sensitive to the ammonium ion, but even more so to free ammonia… Nitrate... was only slightly toxic to both species.”

Kim, Lee, Cha and Keller (2008) indicate that a concentration of free ammonia (NH3) between 30-50 mg NH3-N/l inhibits Nitrobacter, while Nitrospira is inhibited at 0.04-0.08 mg/L. As Nitrospira ceases metabolic activity at small concentrations of free ammonia, the authors suggest that Nitrobacter is the predominant genera responsible for the oxidation of nitrite. At a temperature of 27.5 degrees Celsius (80.6 degrees Fahrenheit and at a pH of 7.5, a total ammonia (NH3 + NH4+) concentration of 1,736 mg/l is required to reach a free ammonia (NH3) concentration of 30 mg NH3-N/l.

(3) 5 ppm nitrite will stall a cycle. MYTH!

Short answer: 5 ppm nitrite by itself won’t stall a cycle. Very high nitrites (far more than is ever seen a household aquarium) is required to a stall a cycle.

Long answer: As Meiklejohn (1954) notes: free ammonia is toxic to Nitrobacter, while nitrite is toxic to Nitrosomonas.

However, Anthonisen, Loehr, Prakasam and Srianth (1976) find that it is not so much nitrite itself that inhibits the oxidation of ammonia, but rather the presence of free nitrous acid, to which nitrite protonates in acidic media. The authors report that free nitrous acid inhibits ammonia oxidation at concentrations of 0.22-2.8 mg/L. At a temperature of 25 degrees Celsius (77 degrees Fahrenheit) and at a pH of 7.5, a nitrite concentration of 4,709 mg/l is required to reach a 0.22 mg/l free nitrous concentration.

(4) Water changes aren’t necessary. MYTH!

Short answer: Well, sort of a myth. Beneficial bacteria require micronutrients, particularly phosphate, in order to grow and most of these are in tap water. At least one water change mid-way through a cycle is important to replenish these nutrients. A water change is also the simplest way of raising pH that has fallen too low.

Long answer: Kumar and Nicholas (1981) underscore the importance of adenosine triphosphate (ATP), of which a component is phosphate, for Nitrobacter agilis' “metabolism and growth”.

Purchase (1974) demonstrates that a phosphate deficiency significantly inhibits nitrite-oxidising bacteria more than ammonia-oxidising bacteria, and that the deficiency results in an accumulation of nitrite.

(5) Low pH can stall a cycle. FACT!

Short answer: Nearly all the beneficial bacteria in your tank will prefer slightly alkaline conditions, from a pH of 7.5 to 8.5, eventually shutting down at 6 (but not dying). While we tend to think that high ammonia or high nitrite caused a cycle stall, it's most likely that low pH caused it.

In fact, a fall in pH is a natural part of cycling: the process of converting ammonia into nitrite lowers pH and in tanks with low buffering capacity, the water may turn quite acidic. Any accumulated nitrite in this acidic water can then turn into nitrous acid, which makes the tank even more acidic. Increasing kH (by adding crushed coral, cuttlebone or sodium bicarbonate) or performing water changes are both ways to raise pH.

Long answer: Fumasoli, Morgenroth and Udert (2015) indicate that while ammonia- and nitrite-oxidising bacteria are widely observed to have decreasing metabolism in acidic environments, they report that the reasons for this phenomenon are not well understood.

Suzuki, Dular and Kwok (1974) reported that the protonation of ammonia into ammonium ions at low pH is the primary reason for reduced activity, as ammonium is unable to diffuse across cellular membranes for metabolism by ammonia-oxidising bacteria.

However, Wett and Rauch (2003) finds that the low concentration of ammonia at low pH is overstated, and that it is more likely the formation of H2CO3 in acidic media and its volatisation as CO2 reduces the availability of total inorganic carbon necessary for ammonia oxidation. In addition, Gieseke, Tarre, Green and de Beer (2006) suggest that ammonia oxidising bacteria possess ammonium transporters that nevertheless enables the metabolisation of ammonium ions even in acidic environments.

(6) You need to dose 4 ppm of ammonia so that enough beneficial bacteria grows for the fish’s bioload. MYTH!

Short answer: Most fish produce very little ammonia. Dosing 2 ppm is far more appropriate and allows buffering for additional ammonia produced by decaying food, plants and other organic matter.

Long answer: Tal, Nussinovitch and van Rijn (2003) conducted experimentation regarding the denitrification of nitrate in aquariums featuring goldfish (Carassius auratus) and Mozambique tilapia (Oreochromis mossambicus). Their data suggests that these species, when fed a diet consisting of 40% protein and comprising 0.5% of their total biomass, produce approximately 0.07 mg of ammonia per day per gram of fish biomass both in respiration and in the bacterial decomposition of waste. Their 100 litre test aquarium of 20 goldfish (390 g of fish biomass) would have produced 0.273 mg/L of ammonia per 24 hours. It is salient to note that “over the experimental period, ammonia and nitrite concentrations were below detection limits (0.01 mg of NH4-N/L, 0.001mg of NO2-N/L).”

Experiment parameters would enable a bacteria colony with an ammonia oxidation rate of 4 mg/L of ammonia per 24 hours to support the ammonia excretions from 4.3 kg of the sampled fish within a 75 litre aquarium.

References

Anthonisen, A., Loehr, R., Prakasam, T., & Srinath, E. (1976). Inhibition of nitrification by ammonia and nitrous acid. Journal (Water Pollution Control Federation), 48(5), 835-852.

Bollman, A., Bar-Gilissen, M., & Laanbroek, H. (2002). Growth at low ammonium concentrations and starvation response as potential factors involved in niche differentiation among ammonia-oxidising bacteria. Applied and Environmental Microbiology, 68(1), 4751-4757.

Bollman, A., Schmidt, I., Saunders, A., & Nicolaisen M. (2005). Influence of starvation on potential ammonia-oxidising activity and amoA mRNA levels of Nitrosospira briensis. Applied and Environmental Microbiology, 71(3), 1276-1282.

Fumasoli, A., Morgenroth, E., & Udert, K. (2014). Modeling the low pH limit of Nitrosomonas eutropha in high-strength nitrogen wastewaters. Water Research, 83, 161-170.

Gieseke, A., Tarre, S., Green, M., & de Beer, D. (2006). Nitrification in a biofilm at low pH values: Role of in situ microenvironments and acid tolerance. Applied and Environmental Microbiology, 72(6), 4283-4292.

Kim, D., Lee, D., Cha, G., & Keller, J. (2008). Analysis of ammonia inhibition of nitrite oxidising bacteria using a dissolved oxygen respirometer. Environmental Engineering Research, 13(3), 125-130.

Kumar, S., & Nicholas, D. (1981). Assimilation of inorganic nitrogen compounds by Nitrobacter agilis. Journal of General Microbiology, 128, 1795-1801.

Meiklejohn, J. (1954). “Some aspects of the physiology of the nitrifying bacteria”. In Autotrophic Microorganisms. University Press, Cambridge.

Purchase, B. (1974). The influence of phosphate deficiency on nitrification. Plant and Soil, 41, 541-547.

Suzuki, I., Dular, U., & Kowk, S. (1974). Ammonia or ammonium ion as substrate for oxidation by Nitrosomonas europaea cells and extracts. Journal of Bacteriology, 120(1), 556-558.

Tal, Y., Nussinovitch, A., & van Rijn, J. (2003). Nitrate removal in aquariums by immobilized Pseudomonas. Biotechnology Progress, 19(3), 1019-1021.

Wett, B., & Rauch, W. (2003). The role of inorganic carbon limitation in biological nitrogen removal of extremely ammonia concentrated wastewater. Water Resource, 37(5), 1100-1110.

 

What about high nitrates? Anything about that?

 

Thanks for posting this.

 

Can also greatly speed up the cycling process compared to traditional methodology:
How To Use Stability and Prime? | Water Supplements Forum | 330232

I recently experimented with this and was successful.

 

What about high ? Anything about that?

There's not much information about the effect of high nitrate concentration on nitrifying bacteria. The only literature I could find was from Meiklejohn (1954) that nitrate is "slightly toxic" to both nitrosomonas and nitrobacter. But the author didn't go into detail about how much nitrate is too much nitrate, nor did he describe the mechanism of action for nitrate toxicity on bacteria.

In practice, nitrates are more likely to be toxic to fish before ever reaching concentrations sufficient to affect nitrifying bacteria, and any water change done to reduce nitrates for the benefit of fish will benefit the bacteria.

 

Sticky this post. Great stuff.

 

Does a high temperature actually help?

 

Does a high temperature actually help?

Good question.

 

Does a high temperature actually help?

It certainly does! Grunditz and Dalhammar (2000) report the following: "the highest activity was found at a temperature of 35C for Nitrosomonas and at 38C for Nitrobacter." These are the upper thresholds for optimum temperature, and in reality beyond the scope of aquarium heaters. But their journal article suggests temperatures between 25C to 30C are optimal for bacteria metabolism and growth.

 

I've included another little mythbuster which I hope others find useful (I've also edited this post into the opening post):

(6) You need to dose 4 ppm of ammonia so that enough beneficial bacteria grows for the fish’s bioload. MYTH!

Short answer: Most fish produce very little ammonia. Dosing 2 ppm is far more appropriate and allows buffering for additional ammonia produced by decaying food, plants and other organic matter.

Long answer: Tal, Nussinovitch and van Rijn (2003) conducted experimentation regarding the denitrification of nitrate in aquariums featuring goldfish (Carassius auratus) and Mozambique tilapia (Oreochromis mossambicus). Their data suggests that these species, when fed a diet consisting of 40% protein and comprising 0.5% of their total biomass, produce approximately 0.07 mg of ammonia per day per gram of fish biomass both in respiration and in the bacterial decomposition of waste. Their 100 litre test aquarium of 20 goldfish (390 g of fish biomass) would have produced 0.273 mg/L of ammonia per 24 hours. It is salient to note that “over the experimental period, ammonia and nitrite concentrations were below detection limits (0.01 mg of NH4-N/L, 0.001mg of NO2-N/L).”

Experiment parameters would enable a bacteria colony with an ammonia oxidation rate of 4 mg/L of ammonia per 24 hours to support the ammonia excretions from 4.3 kg of the sampled fish within a 75 litre aquarium.

I just want to emphasise that 4 ppm of ammonia is enough to convert the ammonia produced by 9.5 lb of goldfish in a 20 gallon aquarium!

 

High nitrite won't stall a tank but will kill/severely injure the fish inside.

 

High nitrite won't stall a tank but will kill/severely injure the fish inside.

Fortunately this thread is about fishless cycling.

 

Fortunately this thread is about fishless cycling.

Totally knew that. Ignore my comment XD

 

Totally knew that. Ignore my comment XD

That's quite all right! It's important to note it regardless, in case someone misinterprets what I wrote and ends up with 10 nitrites in their fish-in cycling tank.ead:

 

That's quite all right! It's important to note it regardless, in case someone misinterprets what I wrote and ends up with 10 nitrites in their fish-in cycling tank.ead:

OMG! I would kill myself with that high of nitrites!

 

This is very helpful and gives me answers I couldn’t find easily. I’ll definitely use this information to help with the my first cycle.