While this will clearly not apply to those who have sterile, bacteria-free interior tank surfaces, or horrible living conditions of the gravel where bacteria cannot survive, and while those with large filtration systems may well be fine, others among us do need to be aware that the removal/substitution of matured substrate and its attendant load of nitrifying bacteria from a tank - or the too-long shutdown of a filter - may have the potential to cause ammonia spikes for which a careful watch should be kept.
Thanks are due to andywg for earlier pointing out the discovery of the importance of certain beneficial bacteria by Dr. Hovanec, who explains below that a major gravel cleaning can disturb the bacteria on the gravel, which should then be replenished.
http
/drtimsaquatics.com/Helpful_hints/On...ndOnlyFAQs.html
Dr. Timothy A. Hovanec, the founder of DrTim’s Aquatics, is considered to be one of the World’s premier authorities on nitrifying bacteria in aquaria and closed aquatic life-support systems. Dr. Hovanec’s research was the first to show the importance that previously unknown species of ammonia- and nitrite-oxidizing play in the nitrification of tropical fish aquaria and other recirculating systems. Dr. Hovanec holds over ten U.S. and foreign patents related to nitrifying bacteria and their application to freshwater and saltwater aquaria. This combination of original research and the practical application of that research means that Dr. Hovanec is uniquely qualified in the tropical fish hobby to answer general questions about nitrification in aquaria and specific questions about his new product for jump-starting nitrification in aquaria -- DrTim’s One and Only Nitrifying Bacteria. ...
... Use One & Only when setting up a new tank and after major environmental changes to your aquarium. Examples of major changes include a disease treatment with antibiotics or chemicals that are harmful to the nitrifying bacteria, after a major gravel cleaning which can disturb the bacteria on the gravel and after a failure of the filter. ...
As biologists have shown, nitrifying bacteria typically attaches to aquarium surfaces, even to those with properties not superficially appearing suitable, due to biofilm properties described below.
The amount of beneficial bacteria present within a filtered, cycled tank is sufficient that there is potential for an ammonia spike after removal of too high a level of whole tank nitrification.
For those preferring not to wade through the scientific article on biofilm attachment of nitrifying bacteria posted earlier:
Excerpts:... all the surfaces in the aquarium tend to "pull" the bacteria from the water.... ' "The greatest population of bacteria is in the gravel" '
http/www.skepticalaquarist.com/docs/biofilm/devbio.shtml
Development of the biofilm.
In a newly set-up aquarium, the first bacterial colonists and germinating algal and fungal spores have already begun settling on every available surface within hours of first filling the tank. With them, the processes that build up the living biofilm community have begun.
Few bacteria remain free in the water column, many fewer than there are in the moist films in soils, for instance. Solid surfaces present the only secure sites for making a microscopic living. Any bacteria present in the water tend to be drawn to surfaces and adhere to them. Several forces are involved. Even in very still waters, isolated bacteria are unlikely to settle on horizontal surfaces by sedimentation alone. Brownian motion, caused by the random buffeting of molecules, is ordinarily involved in bacterial settling, and once bacteria have come very near to surfaces, various fluid dynamic forces take effect: van der Waals forces and electrostatic interactions. Bacteria become irreversibly bound to surfaces, in processes broadly analogous to adsorption of molecules to surfaces. So all the surfaces in the aquarium tend to "pull" the bacteria from the water. Bacterial populations in open water are likely to be adhering to free-floating particles of organic floc or colloidal silt.
The accumulation of bacteria on surfaces isn't just passive, either. Nutrients also tend to bind to surfaces, and bacteria actively move towards nutrients, a reaction that bacteriologists call chemotaxis. Once attached to a surface, bacteria have mastered the art of clinging. They exude coatings made of sticky proteins assembled from amino acids and starches built of linked-up sugars, and their communal life-processes are continually renewing these exudations. The polysaccharide matrix bears a light negative charge, which tends to attract positively-charged cations, including some nutrients. The stringy, sticky, spongy, flaky, water-penetrated polysaccharides accumulate into a labyrinthine protective environment in which bacterial communities thrive. Additional bacterial nutrients are adsorbed to these gummy surfaces. Anti-bacterials, even chlorine, are rendered much less effective by this protective sugar-based envelope, which bacteriologists like to call the glycocalyx, which is Greek for, um, "sugar-based envelope."
The spongy structure continues to build up, eventually becoming hundreds of times thicker than the size of a single bacterium. Deep within a matured biofilm, even anaerobic bacteria find microzones that are secure from the damaging effects of oxygen. This structure and the community that lives on it and within it is called the benthos when it's accumulated in and on the bottom sediment, or more generally the biofilm. This is the stuff German aquarists call Aufwuchs, which could be translated "overgrowth." The bacterial communities in the biofilm and in water trapped within the substrate provide the energy that drives all the recycling of organic and inorganic substances within the aquarium's ecosystem. This same biofilm forms in the woven crimped fibers of the rotating biowheel, so you'll find the description of bio-filtration relevant here.
If you think that a biofilm structure built out of simple sugars linked into polysaccharide chains has a nutritious sound to it, well, you're right. Our snails and otocinclus are more omnivorous than their "algae-eater" titles suggest. A snail passing across what looks to us like a simple algal film is also ingesting a whole community of organisms founded on the bacterial polysaccharides.
"The greatest population of bacteria is in the gravel" is a familiar statement that you often hear when the bacteria at work in filter media are being discussed, but don't forget that even older statement, "A rolling stone gathers no moss." A more nurturing location for those nitrifying bacteria and the others said to be "in the gravel" must be in the floc, or humic compost that is lodged among the grains. If your substrate started out purely gravel, with all silt carefully rinsed out of it, it could take months for this floc to develop. Some additives to substrates for planted tanks are expressly designed to substitute for floc: laterite and colloidal clay and humic compost. Floc and biofilm in the interstitial water of the substrate work like humus in an undisturbed forest soil; they provide homes for most of the bacterial energy that runs the whole cycling system.
So, you won't be surprised to hear that I scarcely ever vacuum my gravel, just siphon off loose surface detritus....
I have included the URLs of two different forums having a link and large alert posted drawing attention to this article following, as it's considered so essential - some excerpts:
... this "ammonia-eating" bacteria start to grow in your tank, particularly your filter and gravel ... ... another sort of bacteria starts to grow in your filter and gravel ... This beneficial bacteria breaks down nitrite (NO2-) ...
... Even in an established tank you can get ammonia or nitrite "spikes", usually because something has killed off your beneficial bacteria. ... ... You over-cleaned your tank, particularly the filter media and gravel, particularly is you didn't dechlorinate your water and particularly if the gravel or filter were out of the water a long time. ... ... A power-outtage stopped your filter or pump from working for a couple of hours (bacteria need oxygenated water to survive).
... . If at all possible, get some matured filter media and/or gravel from a matured tank ... ... Only clean the gravel superficially, of obvious dirt and uneaten food. You want the bacteria to colonise it and actually start to grow ...
http/www.aquariacentral.com/forums/showthread.php?t=108685
http/www.aquariumfish.com/aquariumfish/b...110052-5-1.aspx
NOTICE - This article is very important to new fish-keepers and for tanks that are less than six months old. It is during these early stages that proper filter maintenance is most critical since you are still growing a proper sized Nitrifying Bacteria (N-Bacteria) colony in your filter media and substrate. It is also very important and applicable for tanks over six months old that have limited filtration or overstocking issues. Here is a good article about "The Nitrogen Cycle" to help you understand this "article" further.
http/fish.orbust.net/cycling.html ...
Sections below quoted from the article given in the link:
http/fish.orbust.net/cycling.html
... Beneficial Bacteria
This is where your bacteria come in: fortunately, certain types of bacteria can break down ammonia into a less toxic substance called nitrite (that's with an 'i' - note the spelling, it's important) aka NO2-. After a few days, this "ammonia-eating" bacteria start to grow in your tank, particularly your filter and gravel, and drop your ammonia levels to zero. Phew! But your fish aren't home and dry: nitrite is less toxic than ammonia, but is still toxic and can still kill fish. Thankfully, another sort of bacteria starts to grow in your filter and gravel (albeit a little more slowly than the "ammonia eating" bacteria). This beneficial bacteria breaks down nitrite (NO2-) and turns it into nitrate (NO3+) - note the 'a'. Nitrate is only harmful in quite high levels, which can be controlled by regular partial water changes, and is useful to aquatic plants as a fertiliser. This process is called the Nitrogen Cycle, and in fish-keepers jargon, a tank where the bacteria are happily munching on ammonia and nitrite is said to be "cycled". ...
... Can a cycled tank un-cycle again?
Even in an established tank you can get ammonia or nitrite "spikes", usually because something has killed off your beneficial bacteria. This could be for several reasons:
1. You forgot to dechlorinate your water when you did a water change. Chlorine kills bacteria!
2. You over-cleaned your tank, particularly the filter media and gravel, particularly is you didn't dechlorinate your water and particularly if the gravel or filter were out of the water a long time.
3. Some filter companies recommend you change the filter media every month (Well they would say that, wouldn't they??? ). Not only is this an expensive waste of time quite often (filter sponges usually just need a rinse in some old tank water), you could be removing the beneficial bacteria. If you want to replace a filter insert, leave the sponge or floss in the tank for a week or so beforehand.
4. A power-outtage stopped your filter or pump from working for a couple of hours (bacteria need oxygenated water to survive).
5. You over-loaded the bacteria in your tank's ability to break down the fish waste, for instance by suddenly over-stocking your tank, particularly with messy fish.
6. A tub of food has fallen into the tank and gone bad, thus overloading the beneficial bacteria's ability to cope.
How to save the day (and the fish) with an un-cycled aquarium
OK, so you didn't do Fishless Cycling or you did scrub out your matured tank and now your fish are dying and nothing's breaking down that ammonia and nitrite. What do you do now?
Here's what I do to give my fish the best chance:
1. Immediately do a 10-15% water change with dechlorinated water and continue to do this at least once daily until your tank is cycling (i.e. ammonia and nitrite are at zero).
2. Test the water daily for ammonia and nitrite until the values are holding at zero for several days running. If levels are high, do an immediate, extra water change.
3. If at all possible, get some matured filter media and/or gravel from a matured tank and put it in your tank, suspended in an old stocking. This will hopefully impregnate your new tank with the beneficial bacteria. One lady successfully used floss from a relative's fish pond to colonise her new tank! (you have to be careful that what you use is clean and free from pathogens, of course).
4. Keep good aeration in the tank both to help the fish a little and to oxygenate those beneficial bacteria.
5. Avoid using medications, if at all possible, as many medications kill off beneficial bacteria. Your fish may well get ick, fungus or other infections due to the stress of the ammonia and nitrite but the priority is to get that water quality as good as possible.
6. If you have delicate fish in the tank, such as plecos, corys or other bottom dwellers, tetras, pencilfish etc. try to re-home them temporarily, such as asking the Local Fish Shop to look after them until your tank is cycled (after all, chances are that they got you in this mess in the first place).
7. Live plants can directly use ammonia, so if you can, put some cheap aquatic plants in the tank, such as elodea or giant vallis.
8. Don't feed your fish at all if your ammonia readings are high, and only feed bare minimum rations every other day, until the tank cycles. This will cut down on the ammonia the fish produce. Since fish are cold blooded creatures and don't need the calories of a mammal they can go several days without food anyway, and the occasional fast is good for them. Your fish may not be very hungry anyway so do be careful not to feed more than the fish can eat and clean up uneaten food immediately, before it rots and produces even more ammonia.
9. Only clean the gravel superficially, of obvious dirt and uneaten food. You want the bacteria to colonise it and actually start to grow. Also, don't swap out your filter at this point - if it gets blocked, just clean it enough to unblock it, in used tank water. ...
Excerpt from below: ... Nitrifying bacteria are usually abundant in the gravel substrate or filters of an established aquarium; so many hobbyists use a small amount of this as a bacterial seed. ...
http/members.optusnet.com.au/chelmon/Newtank.htm
... When an aquarium system is first setup or restarted after cleaning, time must be allowed for bacterial colonisation of the biofilter. This is a critical time in aquarium systems, because ammonia levels may increase faster than their removal. Nitrification is often started by artificially adding ammonia, such as ammonium chloride, into the system thereby allowing establishment of the nitrifying bacteria prior to stocking with fish. This would also be expected to encourage growth of autotrophic bacteria because without an organic load, competition for attachment surfaces from faster growing heterotrophic bacteria would be minimal. However, the effect of exogenous addition of ammonium chloride can extend the cycling time dramatically; in some cases, as much as 50~60 days.
It may be advantageous to pre-activate the cycle. Pre-activation is accomplished by seeding the filter(s) with nitrifying bacteria. Seeding of nitrifying bacteria has a positive effect on the nitrification process by improving performance and stability. Nitrifying bacteria are usually abundant in the gravel substrate or filters of an established aquarium; so many hobbyists use a small amount of this as a bacterial seed. Experience has shown that seeding filters with filter media from established filters can significantly reduce new system start-up times. The addition of 10% wet filter media from an established system can reduce the start-up time to around 4~7 days compared to 20~25 days for ammonia removal and a similar time scale for nitrite removal. ...
Excerpt from below:
...ammonia spikes can also occur in mature home aquariums, after gravel substrate or bio-media is cleaned or replaced. ... ... clean aquarium gravel in sections with each water change instead of cleaning the entire substrate floor in one marathon session. ...
http/www.liveaquaria.com/PIC/article.cfm?aid=35
... POSSIBLE CAUSE: A decrease in your aquarium's beneficial bacteria population. These bacteria are necessary to the nitrogen cycle, in which ammonia is broken down. Ammonia spikes are most commonly associated with newly established systems where too many fish are added before a suitable bacteria colony is established. However, ammonia spikes can also occur in mature home aquariums, after gravel substrate or bio-media is cleaned or replaced.
RECOMMENDED SOLUTION: Bacterial additives, such as our Water Repair™ Colonize help replenish beneficial bacterial populations. Simply add the correct amount to your aquarium while setting up a new system or on a regular basis after routine cleaning in established systems. Also, minimize the amount of beneficial bacteria removed from your aquarium with each cleaning. To do so, use a Python No Spill Clean 'N Fill to clean aquarium gravel in sections with each water change instead of cleaning the entire substrate floor in one marathon session. Similarly, do not clean or replace all of your filter media at once or when performing water changes. Replace filter media in stages to allow biological and mechanical media to retain existing beneficial bacterial population. ...
... The guy at the LFS sold me some "Instant Cycle" product that contains the beneficial bacteria. Do I still need to cycle my tank?
There are a variety of bacteria products on the market which claim to be able to increase the speed at which your tank cycles (note: none of them claim instant cycling, whatever LFS employees may say). Personally I can't see how they could work, since the bacteria require a source of ammonia and oxygenated water, but even if they can be held in some sort of "suspended animation", that still doesn't get around the fact that they can't instantly colonise your gravel and filter. Colonisation takes time! ...
Filter manufacturers might like you to have an idea that their filters alone contain the beneficial bacteria which propagates throughout your tank and populates your substrate, and that whole tank/gravel nitrification therefore doesn't matter.
The principles established by biologists tell us differently, as does the experience of many; the removal of too high a level of beneficial bacteria from within the filtered tank does have the potential to trigger ammonia spikes.
Personally, I think it's worth keeping in mind.
Certainly, a little time for consideration never hurts.
