# increasing heterotropic bacteria population or activity in NPT



## tantaMD (Dec 23, 2011)

hi everyone, i'm curious about a thing here. we all know in NPT the main CO2 source is the decomposition process of organic substance by heterotropic bacteria. As an NPTers we have several ways to put the CO2 factor into the max condition without doing artificial CO2 injection. Those usual ways are decreasing the water flow, siesta period lighting, and heavy fish feeding. But i think those ways actually work by saving CO2 and get plantsto use CO2 more efficiently. About heavy fishfeeding, to put it simple about decomposition process we can say it depends on two things the material to decompose and the bacteria that doing it. So in my opinion increasing the fishfood load without increasing the amount of bacteria or the bacteria activities will do only little help here. So is there any exact ways to increase the heterotropic bacteria population or increasing its activities??? I think in that way it can be very sinergistic with increasing the fishfood load. Looking forward for ur comments, ideas, and experiences . Regards from Indonesia :wave:


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## HeyPK (Jan 23, 2004)

Increasing the fish food will cause an increase in CO2 production. If the fish eat it all, they will grow faster, respire more, and will produce more CO2. If there is leftover food, the bacteria will consume it, producing more CO2. Leftover food will cause a rapid increase in the bacterial population. If they run out of food, bacteria will reduce their metabolism. Bacteria can shut down their metabolism when food is absent and can go without food for years without dying. When food is present, bacteria multiply rapidly and are metabolically active. When food is absent, bacteria stop growing and multiplying and basically shut down.


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## tantaMD (Dec 23, 2011)

thanks for the info HeyPK , usually i feed my fish twice a day, they are all very greedy, i can hardly found a leftover usually. So, is there other conditions beside plentiful organic material that can stimulate bacterial growth? Does the fish poop contains relatively the same amounts of organic material for the bacteria? Thanks for being the first to post on my new thread


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## HeyPK (Jan 23, 2004)

Different kinds of organic matter vary in regards to how fast bacteria can utilize it as food. Fish droppings will have a variety of kinds of organic matter, some of which can be utilized more rapidly by bacteria, and some of which will be more resistant to bacterial enzymes. Ultimately, all naturally produced organic matter will be reduced to CO2 and minerals by bacteria, but there will be some organic matter that may take many years to be broken down. The mulm that accumulates in a fish tank is quite resistant and might take many years to be broken down. It would be a very slow producer of CO2. 

If you have a lot of plants that, in bright light, respond well to high amounts of CO2, it does not work to try to produce all that CO2 by throwing in food that stimulates the growth of bacteria. The bacteria will use up the oxygen in the water faster than it can diffuse in from the surface, the tank will become anaerobic and the bacteria will switch to fermentation, producing alcohols and other toxic byproducts. That is why aquatic plant growers use external sources of CO2. The kinds of aquatic plants that are well adapted to being submersed do quite will with the CO2 levels produced by normal populations of fish in the tank. However, there are many other decorative aquarium plants that are better adapted to being emersed, but can tolerate being submersed. Aquatic plant hobbyists have discovered that these plants will grow a lot faster if given higher levels of CO2 that has to be supplied externally.


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## tantaMD (Dec 23, 2011)

correct me if im wrong, so by the info you gave i conclude that to get more CO2 by this method the fishfood load should be increased in a step ladder fashion in harmony with the growth of plant mass. Because the more plant mass means the more O2 by photosyentesis. Of course unlike external CO2 injection, this methodhas its limits, and i think knowing the limit is what important to drive this method to its max. The easy sign of O2 depletion is when the fishes gasping in the surface. But to use that sign as the limit's mark we have to know which one comes first? the frementation of bacteria or the suffocation of the fishes?? Im really lucky to have someone with knowledge like you posting on my thread


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## Michael (Jul 20, 2010)

It is important to remember that O2 content and CO2 content are not directly related--neither excludes the other, within limits. So paradoxically, increasing O2 content and uniform distribution to all parts of the aquarium helps to maintain adequate CO2 levels.

This works by maintaining optimum aerobic conditions for the bacteria. As long as the bacteria have all the O2 they need, they will decompose the organics rapidly and produce more CO2 through respiration.

The way we maintain good O2 distribution is through good water flow and circulation to all parts of the aquarium. Many people worry about loss of CO2 through surface agitation. If the flow in the aquarium is smooth and laminar, not turbulent, and excess surface agitation is avoided, then CO2 loss at the surface is minimized. Under these condtions, the CO2 loss at the surface is probably not significant in tanks without CO2 supplementation. CO2 levels can then rise above equilibrium with the atmosphere.

So as you point out, it is a balancing act. And really the only way to know when you have achieved the balance is through careful observation of the aquarium.


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## HeyPK (Jan 23, 2004)

Also, covering the tank with a glass top reduces CO2 loss.


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## tantaMD (Dec 23, 2011)

thanks  , you guys really helping here. Come to think of it. I felt what we discuss here relatively contradictive with siesta period lighting that miss walstad suggest in her book. Miss Walstad suggests to take a blackout time like about 4 hours in the middle of lighting periods to give the bacteria times to catchup with the plant's CO2 absorption. In that way we can prevents CO2 depletion in the end of our lighting period. But from our discussion i would predict that in that blackout period there is an O2 competition between plants, fishes, and bacterias. which will leads to an O2 depletion state. Which then will lead to fermentation of the bacteria. But still miss walstad has a superbly thriving tanks. My friend in indonesian aquascape forum tried the siesta period with blackout time like about 5 hours, half of the fishes get sick some even dies. I also try the siesta period with blackouts for 2 hours recently this week, all fishes seems doing fine, of course it is to early to see the result in the growth of my plants


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## HeyPK (Jan 23, 2004)

With additions of CO2 to your aquarium by whatever method---Do It Yourself with yeast fermentation or the higher tech method with a bottle of compressed CO2 and a regulator, you do not need to worry about CO2 running low during the day. If you have a lot of fish, you do not need to worry. If you have a very light fish load and the CO2 runs low during the day I still do not see the value of turning the lights down, other than maybe to save on electricity costs. CO2 depletion is not particularly harmful to plants except that it reduces the rate of photosynthesis. If CO2 is limiting, some species of plants will turn out to be much better at getting the available CO2 than others. The plants that are better competitors will grow and the others will not.


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## tantaMD (Dec 23, 2011)

thanks heyPK, by the way i have two NPT in my home. One has been going one for a year thrive succesfully almost without any interventions, the other i set it up 3 months ago. The main reason i set the 2nd tank was that i have curiosity about keeping the so called difficult plants in NPT. People's opinion about NPT usually "it's only work for easy plants". But all the aquatic plants wether easy or difficult thrives in nature by the el natural methods too right? . i've seen some people having success keeping these difficult plants in their NPT, the latest is in the AGA 2011 aquascape competition which he/she succeeded thriving hairgrass and glosso in outdoor tank. And diana walstad succeeded thriving rotala macrandra in an NPT. I also try to keep r. macrandra in my 2nd tank, u can check my 2nd tank in indonesian el natural thread . That is the reason why i try to search methods to make it thrive. i know if i just leave it and wait like what i had done to my first tank, this 2nd tanks have a big chance to succeed. But big chance the r. macrandra will not survive too . so i try to reach the optimal condition that an NPT can have


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## activesize (Jun 26, 2011)

In a normal and established tank with adequate current flow there is no chance of any bacterial fermentation affecting water chemistry due to the lights being off at night or during a siesta. The tanks can't even begin to cycle between aerobic and anerobic conditions that quickly just because you turn off the lights at night or part of the day. 

I have used what I call a 'twilight siesta' lighting regime for about a year with good results. Actually, I use a combination of Walstad's siesta regime plus what marine aquarists do with sump (refugium) lighting. That is, they have a refugium where they grow macroalgae with a lighting regime which is reversed to that of the main tank. It's a way of helping to stabilize the oxygen and CO2 levels in both tanks and the concept is exactly the same in a fresh water system. So, I have actually three tanks plumbed together, although only two is needed, or even a 'hang on back' refugium or 'in tank' refugium can be done with one tank. Of course, instead of macroalgae I am growing ornamental aquatic plants and baby fish in the refugium, which actually, is just another NPT. But, I also have about two hours of 'total' darkness during midday for all tanks and various combinations of 'reversed' lighting for two more hours each day. The result is that photosynthesis is shut down in each tank for four hours each midday, but two of those hours the fish can see reasonably well enough through indirect lighting from the other tanks to be active and swim around. During those two 'twilight' hours the metabolic waste products (oxygen and carbon dioxide) are shared between the various tanks in an optimal manner as directed by the light cycle. The fish and plants all seem to enjoy this pampering, and whatever algae I have will attempt to establish in the refugium but the other tanks seem to be virtually immune to it.


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## tantaMD (Dec 23, 2011)

correct me if im wrong, i think to sum it up, whats matter is how long does it takes of having a poor O2 condition before the bacteria starts fermenting themself, am i right??


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## activesize (Jun 26, 2011)

Happy New Year. Yes, I believe you are correct. In an established system there are always both aerobic and anaerobic bacterial populations present and exuding waste products. However, whether it includes CO2 or alcohols and other fermentation products is missing the point. In a healthy and balanced NPT it makes no difference when you turn the lights off at night or for a siesta period to cause the bacterial populations to shift it's percentages of anaerobic vs. aerobic bacteria. If fish can survive at night then there is no question that aerobic bacteria can survive equally well. There probably has to be a lack of both water circulation and lighting over a much longer period of time resulting in oxygen starvation and a lot of decay in the form of numerous dead fish, snails, and plants for significant changes to begin to occur in the percentages of aerobic and anaerobic bacterial populations. Especially with a larger tank you really have to hit it over the head and try to destroy it's balance and it will be difficult. Snails and bottom feeders will quickly consume any dead fish or excess fish food at the moment it becomes the most decayed and palatable. If the lights don't come on for a few months then perhaps low light plants and algae will become predominant. If they go unfed then fish will eventually consume each other or die but invertebrates will take over, etc. Life goes on.


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## tantaMD (Dec 23, 2011)

Happy New Year too everyone . @ activesize : thanks for ur valuable info


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