Hi all,
The problem with doing it for longer than 2 weeks and not adding fish if you are not adding ammonia, is that the plants and filter bacteria will exhaust their resources and you get a "dip" before you add fish, which can lead to the filter bacteria dieing off due to a lack of "food" for want of a better term.
This is really the point, you always sources of ammonia in the aquarium, as proteins are denatured they are split into their constituent amino acids and as these are further degraded ammonia is released. Fish are an obvious source of ammonia, but chlorophyll is also protein rich, and decomposition processes will release this. Fixed nitrogen (so nitrogen that isn't in the form of N2 gas) is a scarce and patchy resource in natural ecosystems and the organisms that rely on it are adapted to a "boom and bust" existence.
Have a look at <"
New High Tech Setup...">
i'm not saying i would add fish without cycling first, what i am saying, is that if you are not adding ammonia, compost, or ada soil, then you are not really cycling the tank, and once you add fish that will effectively be the propper beginning of your cycle process
This is still looking at ammonia as the most important factor in biological filtration, but it isn't oxygen is, scientists talk about Biochemical Oxygen Demand (BOD) because it quantifies the total amount of pollution. Cycling is an ongoing process, and it never really starts or stops, the more complex ecosystems are the more resilient they become. If you think of cycling as a web, rather than a linear process (with a switch from "non-cycled" to "cycled"), it becomes easier to visualise whether systems are likely to maintain water quality.
If we look at BOD values, clean rivers have a 5 day BOD value of about 1 mg/L, and at 8mg/L they are heavily polluted, and raw sewage averages about 400mg/L. You can only get about 8 mg/L of oxygen into aquarium water (warm water holds less dissolved gases) so you can see that if you want to treat the ammonia in sewage that, as well as a community of nitrifying organisms, you need to constantly replenish the oxygen. We can actually treat sewage with a relatively small volume of bacteria if we get enough oxygen into it. Normally we add air (~21% oxygen), but we can improve the efficiency of nitrification by adding pure oxygen (O2) (like plants do via photosynthesis).
A relatively small wet and dry trickle filter has much more nitrification potential than a big canister filter, mainly because the amount of oxygen that enters the canister is finite, and it can't be replenished in a sealed container. Wet and dry trickle filters have huge gas exchange surfaces, and that is really why they are so good. You can improve a wet and dry trickle filter by planting it, and there is a lot of scientific work on this for effluent treatment using <"
Constructed Wetlands">.
You can make your canister filter even less efficient by stuffing it with media so that it can fulfill the anaerobic denitrification arc (converting NO3 to N2 gas). I'm not even going there, that is a sure recipe for eventual disaster
and you have to make sure your plants are growing really well before adding stock,
but i am not confident in their ability to make up the shortfall, and large water changes would be a necessity.
These are important points, plants only work to improve water quality when they are growing. Submerged plants are CO2 limited, but a floating or emergent plant aren't, when you add a floating plant it starts working straight away. Floating plants are widely used in <"
sewage treatment etc."> in warmer regions, because of their high potential growth rates.
In environments with high inputs of ammonium, such as wastewaters, biooxidation of this substrate increases the oxygen uptake and lowers the pH. Such modifications of the environment not only affect the production of nitrite and nitrate but can also select a different nitrifying community that is perhaps specialized for these new conditions.
I just think it is a speculation to say that an ammonia cycled tank develops the wrong type of microbes, especially considering anecdotal evidence/experience pointing to the contrary. Also, no-one knows what the type of established bacteria/archaea is in their particular tanks.
According to the above study, it doesn't just stall but totally different nitrifying bacteria gets established..
That is right, but I'm pretty sure the community we want is the community is specialised for these new conditions.
I don't know what organisms I have in my tanks, I don't know what the BOD is and I don't know what the exact water parameters are, and nor does any-one else who keeps an aquarium. I could potentially get a snap shot of BOD, dissolved oxygen and reasonably accurate chemical parameter values because I have access to analytical kit in the lab., but even that would only be a snap-shot, and I don't have access to any RNA analysis techniques.
Before the development of RNA libraries we were reliant on culturing bacteria (from sewage treatment etc) to find out what organisms were involved in nitrification, which led to many of the assumptions about aquarium cycling that we now know to be incorrect. It isn't surprising, if you look at raw sewage it is a very different medium, from even very polluted, aquarium water. Dr Tim Hovanec talks about this is in <"
Bacteria revealed">, and there are a number of papers specifically on the nitrifying organisms in aquarium filters which suggest that their assemblage shows a fluid response to varying ammonia loadings, with a stable core of archaea and an ever changing cast of nitrifying bacteria. This is described in <"
Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira">.
cheers Darrel
