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Registered Member
The Nitrogen Cycle
The Nitrogen Cycle
In an aquarium, there are waste products given off by the fish, or by uneaten food or other organics such as plant decay. All contain Nitrogen. Fish give off waste products, including ammonia through the gills. Uneaten food and solid wastes are broken down into ammonia by fungi and many bacteria that we refer to as heterotrophic bacteria.
The ammonia can be in two forms. Toxic (to the fish) ammonia is in the form of NH3 and occurs when the ph is greater than 7.0. Nontoxic ammonia is NH4 and occurs when the ph is below 7.0. Ammonia is very toxic to fish.
Ammonia is broken down into “Nitrites” (NO2) by special bacteria called “Nitrosomonas” bacteria.
Then the Nitrites are broken down into “Nitrates” (NO3) by another special bacterium called “Nitrobacter bacteria”. Nitrates are not harmful to fish unless they become high. The most effective way to keep nitrates low is through water changes.
In a new aquarium very little of the nitrosomonas or nitrobacter bacteria are present, and need time to reproduce to sufficient levels to breakdown their respective nitrogen compounds. The bacteria attach to surfaces in the aquarium such as gravel (if you have it) or the material in the filter, such as sponges that have a large surface area for the bacteria to attach to.
Ammonia levels can start to stress the fish at levels of more than .3 mg/l depending on the ph and the temperature of the water. (Untergasser 1989) To minimize the stress the ph level can be kept below 7.0 and /or water changes can be used to keep the ammonia level below .3 mg/l. Usually the easiest approach is to do water changes. High levels of ammonia may show up on the fish as hemorrhages on the gills. The gills may appear “lilac” in color. (Untergasser 1989)
Nitrite in the water is absorbed by the blood of the fish. This reduces the bloods ability to transport oxygen to the fish’s body. Continuous exposure to nitrite can lead to “brown blood disease”, where the hemoglobin in the blood is bound to nitrite and the fish suffocates from lack of oxygen. Non iodized salt can be added to the water at 2 tbsp/10 gallons water, to help the fish cope with nitrite. Water changes are one of the best ways to cope with high nitrite levels.
When ammonia and nitrite levels reach zero, we refer to the aquarium as being “cycled”. This is having enough of the proper bacteria in the aquarium to convert the organics into nitrate. This usually takes from 4 to 6 weeks. Speeding up the cycle can be achieved through addition of gravel or filter media from an already cycled aquarium or by the use of *bacteria products sold at a pet shop.
Sources
Handbook of Fish Diseases by Dieter Untergasser, TFH Publications, Inc 1989
Maintaining a Healthy Aquarium by Dr. Neville Carrington, Salamander Books 1985
Internet resources
http://faq.thekrib.com/begin-cycling.html
This site has a good chart on cycling time and effects of ph and temp on ammonia toxicity.
hth
Ardan
Last edited by Ardan; 02-19-2014 at 07:35 PM.
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Registered Member
Re: The Nitrogen Cycle
Hi Ardan:sunshine:
This is one of the best articles you've written and one I hope everyone reads. It clearly states the nitrogen cycle - the most important process in the aquarium!
Please put a sticky on it so future memebers can find it easily.
Carol
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Registered Member
Re: The Nitrogen Cycle
Thank you for the kind words Carol!
I hope it helps people understand the nitrogen cycle a bit.
Thank you very much!
Ardan :sunshine:
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Re: The Nitrogen Cycle
Well typed steelhead do you publish science alot?
if you are interested in more data on the bacteria in the cycle Tim Heanovac From Tropical Fish Mag. Did his Phd on the topic and i saw an article about it.
I think he did a bunch of PCR's on the typical flora of the filtrers.
Cobalt
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Registered Member
Re: The Nitrogen Cycle
Hi Cobalt,
Thank you for the kind words. Actually I'm a welder/metal fabricator. The only writing I do is here at Simply. I am just trying to help people understand the hobby better and I like the sciences of this hobby, so it is interesting to me to research and share the information.
I will have to look for that issue of "Tropical Fish Magazine". Is that the June issue?
Thank you very much!
Ardan :sunshine:
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Re: The Nitrogen Cycle
Ardan,
Just finished reading your thread. OUTSTANDING!!!
Lots of real good and useful information.
Miles
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Administrator
Re: The Nitrogen Cycle
Hi Ardan ,
Very Nice write-up! and references. They get better and better!
Hi cobolt,
I have read alot of Dr.Hovenecs papers. He works for Marine land. There area good number of his papers at that site...
http://www.marineland.com/drtims_reports.html
http://www.marineland.com/reports/13Nitrospira.html
His research is interesting in that it indicates that what we all have taken to be Nitrosomonas and nitrobacter in our aquariums may be a totally different bacteria all together....Nitrospira spp.
...Thats science for you as soon as you think you have all the answers , you realize you need to revise you understandings! ;D
take care,
al
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Re:The Nitrogen Cycle
Ardan,
As usual, you are selecting a very helpful article. It's good to be kept as reference.
There is only one point which I would like you to clear it up for me:
Those useful bacteria 'Nitrosomonas & Nitrobacter' are very slow in replication and it takes them around 4-6 weeks to catch up with nitrite production.
The question is, daily 30% water change will not slow the replication of those beneficial bacteria beside the difficulty the Discus might face in adaptation with the new water. Most of common books for fresh water fish keeping recommends W.C. weekly 10% or bi-weekly 20%?. Is this rule dose not aplly for Discus.
???
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Registered Member
Re:The Nitrogen Cycle
Hi,
Daily wc may keep the ammonia and nitrite levels low, thus slowing the replication of the nitrosomonas and nitrobacter bacteria. But it is still best for the discus to keep the ammonia and nitrite low.
This is one of the reasons I like a fishless cycle of the aquarium before adding fish, so that the fish and I do not have to deal with ammonia/nitrite stress.
Daily wc are best for discus IMO. I can see a great improvement in my discus by doing wc.
hth
Ardan
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Re:The Nitrogen Cycle
Very useful summary on nitrogen cycle, Ardan. Thanks!
When I first noticed Untergasser's article mentioning ammoina was in an non-toxic form with PH below 7, I started wondering whether it implied our tank was free of ammonia problem if we keep the PH below 7. So no need to test the PH level then?
Karl ???
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Re:The Nitrogen Cycle
Hi guys and gals, not sure here, but isn't NH4 ammonium, not ammonia NH3, I stand corrected on this one.
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Re:The Nitrogen Cycle
Oh yes, you are right. NH4+is ammonium.
Karl
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Re:The Nitrogen Cycle
Optimum pH for sustainable biological activitiy (microflora) in the aquarium is stated to lie between pH 6.5 and 8.0. Bacteria tolerate higher temperature's (30C) and lower Ph value's (down to 4.5) than they do with the same Ph values but at a lower temperature (15C). Bacteria in Ph values of lower than 3.5 regardless of temperature virtually cease to exist.
"Why isn't water just water anymore" ???
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Registered Member
Re:The Nitrogen Cycle
Ardan : Thankyou ........plain and simple.
Jim
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Re:The Nitrogen Cycle
Ardan
Great stuff. Thank you.
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