study & questions - Page 2 - Tropical Fish Keeping - Aquarium fish care and resources
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post #11 of 28 Old 03-24-2014, 11:45 PM
Originally Posted by pop View Post
Hello Mikaila31
“An oxic environment pushes towards oxidation (Ammonia to nitrate as we know). Anoxic the energy potential is different and pushes towards reduction (nitrate to ammonia).” I am not disagreeing with you but only asking a question would not a anoxic environment tend to reduce nitrate to a form of nitrogen gas completing the nitrogen cycle instead of ammonia restarting the nitrogen cycle which is an oxygen intense process.
Yes in an anoxic environment nitrate can be reduced all the way to N2. This certainly does happen to some extent. Tho ammonia is not converted to N2 from what I know. It is nitrate to nitrite to N2(most common at least), but I'm not entirely sure of that. Some Nitrite will go to ammonia some to N2. This nitrogen(as N2) is basically lost to the system in a freshwater environment. N2 is rarely usable by aquatic plant as very few can nitrogen fix, some bacteria can fix nitrogen but again its only going to happen in an anoxic environment were nitrogen is limiting, as its very demanding. So any N2 produced in an anoxic substrate will eventually move back into the oxic layers and eventually into the atmosphere and leave the system, or it will eventually bubble out when physics allow it to. If you have ever paid attention to substrate of a semi-clear lake gases regularly bubble out especially if you disturb them. Nitrogen gas is one component other gases also form in an anoxic substrate due to other nutrient cycles. Nitrate that enters an anoxic environment may leave it before being fully reduced, similarly if nitrite enters an anoxic environment it will still be reduced.
Originally Posted by pop View Post
“Photosynthesis requires energy input, that mostly being sunlight but some comes from the plant as well. The energy input drives the synthesis of sugars. The sugars are now stored energy for the plant. Only when it respires and breaks down the sugars it made does it get energy out of them” again I am not disagreeing with you but I thought that oxygen (respiration) is produced by photosynthesis during the light dependent reaction creating ATP’s glucose sugars are created during the light independent reaction using CO2 the calvin-benson cycle and not part of plant respiration.
Yes you are very correct. The light and dark reactions are what make up photosynthesis in that manner. Water is cleaved to produce the O2, I'm not sure if that is considered a type of respiration or not. By respiration I mean, or was referring to, cellular respiration(glycolysis) which is what happens to the glucose created during photosynthesis(unless they are stored as starch) they under go glycolysis and basically broken back down into water and CO2 again.
Originally Posted by pop View Post
In #7 “Any object in water will have drag on the water moving around it. This means where the leaves and water meet will have the slowest water movement” are you talking about the unstirred area that is sometimes called the boundary layer in fluid dynamics created by friction.

I have been learning up.
Yes the boundary layer is exactly what I am referring to.

One should always be learning

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post #12 of 28 Old 03-25-2014, 08:35 AM Thread Starter
there are some bacteria that can convert ammonium directly to N2. - yes, definitely not common
they were discovered in sewage treatment plants, and i think the bacteria themselves are toxic.

easy to see why not desirable

i stopped looking into that direction when the suggestion that these bacteria are toxic. so i don't remember too much, and when i try to look it up i keep forgetting what it's called. Anammox if curious (i hate looking up that word, i can never spell it right :(


bits i have found for nitrogen fixing bacteria point me towards cyanobacteria, ... much of which is toxic (there are non-toxic strains out if curious - spirulina comes to mind), i'm not sure at all, but i think cyanobacteria convert N2 to ammonia.
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post #13 of 28 Old 03-25-2014, 02:02 PM
I deep sea bed (DSB) was all the rage 10 years ago. And is still in use with many reef type tanks.

But then about 5 years ago some reported all the sudden crashes.

So people started talking much more about refugiums with macro algaes. and also algae turf scrubbers (again).

the DSB works with anoxic bacteria to reduce nitrates to nitrItes then to nitrogen gas.

But if it is not work correctly some evil bacteria can actually further reduces the nitrItes to ammonia.

So you wind up with an aerobic cycle ammonia->nitrItes->nitrates.

and an anaerobic nitrates->nitrItes->ammonia. (plus possibly releaseing some sulfur in the process)

And to top all that off the surface of the substrate has low oxygen (high carbon dioxide) and nitrogen gas. The exact requirements for cyano bacteria. so after a few months of operation, nitrates drop down and then here comes a huge cyano bloom.

so some like me just use FW plants and marine macro algaes so the cycle is:

ammonia->nitrItes->nitrates->plant tissue.

maintain Fw and marine system with a strong emphasis on balanced, stabilized system that as much as possible are self substaning.

have maintained FW systems for up to 9 years with descendants from original fish and marine aquariums for up to 8 years.

With no water changes, untreated tap water, inexpensive lighting by first starting the tank with live plants (FW) or macro algae( marine)

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post #14 of 28 Old 03-25-2014, 02:40 PM Thread Starter
bob, it doesn't sound like you know why DSBs were used, ... nor does it sound like you're familiar with why they were abandoned as a good alternative to keeping reef aquariums healthy. (i could be wrong, don't care, not getting into it farther here)

otherwise, this is a topic that was covered in excessive depth and detail in a thread on another forum to understand and share what was going on.

not something i'm going to get into on here at all. (pending text material - and even then, i'm 'currently' satisfied with what i know to rest assured a DSB is a waste of time & space)
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post #15 of 28 Old 03-25-2014, 04:15 PM Thread Starter
is it right to view biochemical activity (nitrates, CO2, sugars, etc.) as little more than stores of energy ?

a particular chemical has a specific energy value stored within it's bonds, ... to make use of this, enough energy has to be applies to break down or change the chemical to have a predictable energy output that is used by organisms.

would that be right or make it harder for me to understand things later on ?
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post #16 of 28 Old 03-25-2014, 10:55 PM
BSD is something really only discussed for reefs/SW which I know nothing about. FW wise I do keep fairly deep substrates and some are initially quite anoxic due to soil breakdown. I feel typically they stay anoxic but gas production drops off quickly. Most of these tanks are straight topsoil with a sand cap, but one is just 2" of uncapped topsoil. It varies from soil to soil on how they respond and how quickly they establish. You do not need an excessively deep soil to get it go anoxic. Its a natural thing to happen and IMO nothing to be too concerned about. Only difference between sand and topsoil is topsoil has that high initial nutrient breakdown since I don't mineralize them. I've never had issues with cyano bact. except in the exact opposite.... my bare bottom tanks will get cyano sometimes. Main reason in FW at least is cyano loves little to no nitrates, it can out-compete in those conditions because as mentioned above it can nitrogen fix. No matter how anoxic my soil tanks get I make sure the nutrients stay high since my tanks are high demand - high production.

Plants are not a long term nitrogen sink. To assume this you have to assume they are always growing and never limited by any specific nutrient as that can easily slow uptake of others. Also assuming they never die back. The only way this works in nature is from grazing herbivores, which typically are non-aquatic but waterfowl and some mammals. If you think about it, temperate lakes like in the midwest were I live loose most all their plants every winter once the ice sets in. The dieback is down to basically the roots as ice and snow cut out most sunlight as well. Then come mid summer there are some amazing 'towers' of plants easily 20ft tall on one of the clearer lakes I love.

@ flear Yes that is the chemical basis of how an organism works no matter how small or large. Additionally molecules prefer to have lower energy there does not always need to be a biological process involved. Take the ammonia-ammonium association. This happens because at lower pH there is a greater abundance of H+ ions in the water, this changes potential energy of the ammonia. At lower pH/higher conc. of H+ ammonium is more stable and the activation energy to go between the two is low enough it can happen spontaneously on its own. Food webs also follow the basis of energy transfers, so it is a trend throughout the entire system.

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post #17 of 28 Old 03-28-2014, 02:11 PM Thread Starter
acidic conditions in fermentive processes

is it just under anoxic conditions that the substrate is expected to acidify while organics break down ?

i have no idea what is going on in my substrate (nor do i know how it could be tested without messing with it, causing inaccurate readings)

i may be asking a little early, but for things to adicify, wouldn't nutrients be changed and/or displaced in another area that would be more alkaline/base reading ?
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post #18 of 28 Old 03-30-2014, 11:11 AM Thread Starter
Anoxic Environments

the intestines (not to sound gross)
do these count as anoxic environments for potential nutrient cycling ?

(i assume more for larger fish)
i would guess only if the fish have eaten critters that for whatever reason (including hypothetical) have consumed nutrients that would otherwise be removed from whatever nutrient cycle it is a part of due to pH & redox.
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post #19 of 28 Old 03-30-2014, 12:59 PM
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post #20 of 28 Old 03-30-2014, 01:02 PM
Just reread page 1 on oxygen.
Always wondered on my tanks with plants and no circulation why i have high ph yet fish do fine.
Perhaps there is much higher o2 and much lower co2 then if i had circulation.
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