# PH below 6.5 kills bacteria?



## DarkCobra (Jun 22, 2004)

True, there are several reputable research papers saying that as pH drops below 6.5, nitrobacter and nitrosonomas (your biofilter) shut down then die.

And I do observe what appears to be a reduction in the bacterial colony in HOB filters that I use as CO2 diffusers.

But as you have observed, some people run this low without actual problems in real aquariums. Why this is, I don't think anyone knows for sure. In a planted tank, plants can take up the role of primary biofilter, especially with the added growth from CO2. In discus tanks, something else must be responsible; it could be that bacteria adapt over time, or another species we're not familiar with moves in.

But forget the statement about "pH has to drop a full degree to have acceptable CO2" entirely. pH is a logarithmic, not a linear scale. Every 1 point drop from 7.0 represents a _tenfold_ increase in acidity, which makes this rule incorrect, and predicting your final value difficult.

Your tapwater's KH of 3 is plenty of buffering capacity to avoid a pH crash (a rapid, uncontrolled drop in pH, when the ratio of acidicity/alkalinity gets too far out of balance). Stop adding buffers, and you'll probably end up at 6.2-6.4, rather than 5.8. I've run at 6.2 without problems.

So I say go for it. But I would test ammonia levels and watch the tank after the change, just to make sure.


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## jimmah (Feb 16, 2010)

Thanks for the info. I'm gonna give it a try, Everyone else is doing it lol


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## happi (Dec 18, 2009)

so that mean all my good bacteria are dead now, because my PH read yellow (about 6.0) on API test kit, that is with co2 being dosed.


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## stewardwildcat (Feb 24, 2010)

**opinion alert** I would believe that the typical biofilter bacteria may die at a certain pH. However, as in most living systems there are other less efficient bacteria that probably fill some of the space. Combined with plants and the fact that the pH is not exactly the same everywhere you probably have some bacteria that grow as a film near the top of the aquarium.


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## Jeff5614 (Dec 29, 2005)

Here are a few articles on the subject:

http://www.oscarfish.com/article-home/water/71-autotrophic-bacteria-manifesto.html
http://www.thewaterplanetcompany.com/docs/WPC_Nitrification & Denitrification .pdf
http://www.bioconlabs.com/nitribactfacts.html
http://www.pondtrademag.com/articles/ar-154/
http://www.wrights-trainingsite.com/Nitrif1onb.html
http://forum.practicalfishkeeping.c...gU#v=onepage&q=ph nitrifying bacteria&f=false
http://www.americanaquariumproducts.com/Nitrogen_Cycle.html
http://davidcecere.pipidae.org/biocycle2.htm


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## stewardwildcat (Feb 24, 2010)

Your links were truncated and do not all work.


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## Jeff5614 (Dec 29, 2005)

stewardwildcat said:


> **opinion alert** I would believe that the typical biofilter bacteria may die at a certain pH. However, as in most living systems there are other less efficient bacteria that probably fill some of the space. Combined with plants and the fact that the pH is not exactly the same everywhere you probably have some bacteria that grow as a film near the top of the aquarium.


You're probably right. After all, you can wipe out the normal flora for any system including those of the human body and another variety of bacteria will take that place but do they perform the same function as well? Are there interesting and undesirable side effects to being colonized by an opportunistic organism?


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## stewardwildcat (Feb 24, 2010)

Right, efficiency and bi products may be a problem outside of the "usual" Nitrification parameters.


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## Jeff5614 (Dec 29, 2005)

stewardwildcat said:


> Your links were truncated and do not all work.


Fixed just for you  .


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## stewardwildcat (Feb 24, 2010)

Gracias sir!


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## HD Blazingwolf (May 12, 2011)

to sum up most of those links. ph below 6.0 causes the bacteria to go into remission.. eventually they will die. however below 6.5 your bacterial efficiency is also about 30 % what it was compared to 7.0 fish don't die below 6 because the low ph converts the ammonia into a less toxic form. if u raised the ph they would all die. so its a trade off really. in the end plants will still become your final filter.. just depends on how you want the filtering done. i personally like nitrifying bacteria but there are plenty of people that run 5-6 ph tanks with no problems and are very happy with them


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## mordalphus (Jun 23, 2010)

I'd say they don't die completely, just their colonies become very small. I know in shrimpkeeping, especially in Asian countries, they keep the pH very low, between 5 and 6.5 and in order to maintain a good bio filter, they oxygenate the water and provide 5-10 times the bio filtration rated for their tank size.

IE. A 20 gallon tank would be running 3 canisters in a chain rated for a 30 gallon tank as well as 2 sponge filters rated for a 30 gallon tank, or a single sponge rated for a 40 gallon tank.

I myself am running one on tank, a canister rated for 40g, a canister rated for 20g, a sponge rated for a 40g, another sponge rated for a 20g, and a HOB breeder with some ceramic bio media in it.

But that's for shrimp in an unplanted tank, so it's probably quite a bit different from what you're looking into.


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## Hoppy (Dec 24, 2005)

People use lots of CO2 with high light tanks. That must necessarily drive the pH down almost always below 6.5. Those people find they have much less algae problems than if they don't use the CO2, and I would expect the opposite if the low pH was doing significant harm to nitrifying bacteria. Of course, it is always recommended to shut off the CO2 when the lights are off, which should be for about 14-16 hours a day, so any harm to the bacteria may be reversed during that time each day.


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## HD Blazingwolf (May 12, 2011)

Hoppy said:


> People use lots of CO2 with high light tanks. That must necessarily drive the pH down almost always below 6.5. Those people find they have much less algae problems than if they don't use the CO2, and I would expect the opposite if the low pH was doing significant harm to nitrifying bacteria. Of course, it is always recommended to shut off the CO2 when the lights are off, which should be for about 14-16 hours a day, so any harm to the bacteria may be reversed during that time each day.



very true. the bacteria kinda of slows down and quickly comes back to full capacity. this is why well oxygenated tanks are KEY. to good fauna and flora health.


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## JoraaÑ (Jun 29, 2009)

Where to find bacteria in tank?


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## HD Blazingwolf (May 12, 2011)

Joraan said:


> Where to find bacteria in tank?


look everywhere!


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## fresh.salty (Jul 2, 2010)

> Similarly, both the bacteria exhibited maximum growth at
> pH 8.0. At pH 4, 6, and 10 the growth rate decreased
> nearly by 50% (Figures 3 and 4).


From...
Effect of environmental factors on nitrifying bacteria
isolated from the rhizosphere of Setaria italica (L.)
Beauv


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## HD Blazingwolf (May 12, 2011)

not to say your wrong. i cannot at this time because i have insufficient evidence. but are waterborne colonies not different from airborne colonies. both require aerobic conditions but one flourishes better in the different environment. if that is true. would they not be affected differently by other factors. including ph. i would scarecly say we would add neem oil to an aquairum as well.


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## fresh.salty (Jul 2, 2010)

Could be. But I like to base my thinking and conclusions on peer reviewed published papers and not hobby articles. I didn't see a link for anything in this thread to back up the original claim.

Here's a quote from an article that may explain why pH doesn't wipe them out.



> Nitrifying bacteria in soil exist on the surface
> of particulate material and protection from low pH may
> be provided by surface attachment and biofilm formation.
> Growth of Nitrobacter on glass surfaces and on
> ...


From...

AMMONIA OXIDATION AT LOW pH BY ATTACHED
POPULATIONS OF NITRIFYING BACTERIA

It seems obvious to me that there is still some biological activity happening in tanks with lower pH ranges. Again, maybe not nearly as productive in higher pH ranges. Just shows how we might not need them to be working at 100% effectiveness.

Am I wrong to believe that there are natural habitats that fall under the 6.0 threshold?


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## HD Blazingwolf (May 12, 2011)

not at all wrong. there seems to be a niche for every type of life and organism in our world. heck there is stuff that lives in 28 degree water AND THINGS THAT LIVE waaayyy down in the ocean where pressure is extreme...........


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## ray-the-pilot (Jul 5, 2011)

*Who needs bacteria?*

In a well planted tank the plants do all the work removing ammonia. they take it up in preference to NO3


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## jimmah (Feb 16, 2010)

ray-the-pilot said:


> In a well planted tank the plants do all the work removing ammonia. they take it up in preference to NO3


True but the problem now seems to be at the water change with nontoxic ammonia being converted to NH4(i think it was, if not then its NH3) which is toxic b/c at least 50% of the water has just been changed(dosing EI). So it seems to me that at least once a week the fish will undergo ammonia posioning


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## HD Blazingwolf (May 12, 2011)

prime converts it to ammonium the non toxic form  also if u have enough plants you wont see it anyways 

that being said unless ur below 6.. u will still have at least some bacteria normally present in other aquairums doing work.. im unsure of what may grow in lower ph's if any.. but u will still have some


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## mattycakesclark (Jun 11, 2010)

Here are some thoughts from a wastewater perspective. Nitrication is a alkalinity consuming biological process. (Appox 1# ammonia oxidized to NO3 consumes 7.1# of alkalinitty). 
In an aquarium, that water is much much more diluted in term of raw nutrients than wastewater, but alkalinity should still play a role. 
Wastewater plants can run into situations where their pH becomes too low due to the nitrification process. The process in WW treatment is best between a pH of 7.5 - 8.0, but can go as low as 6.5. At 6.0, nitrification is severely limited or stopped all together. 
How this translates to the aquarium world, where NH4/NH3/BOD concentrations are much lower is your guess. 

The link above is a real good read on this : http://www.thewaterplanetcompany.com/docs/WPC_Nitrification & Denitrification .pdf


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## bsmith (Jan 8, 2007)

I inject very high amounts of Co2 in my tanks. In my 37g I often get GW outbreaks not too long after a WC. GW is caused by ammonia being present. Everything that is being said in this thread backs up why I get the outbreaks from time to time.


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## Dave-H (Jul 29, 2010)

I'm steady at 5.8ph, and everything seems to be just fine.


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## nonconductive (Jan 29, 2010)

i've kept mine as low as 5.5 with injection and have had no problems. 

i have read articles where discus freaks will lower their ph into the 4's to combat bacteria infections.


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## HD Blazingwolf (May 12, 2011)

no one said u would have a problem. just that the bacteria might not be working.... plants absorb ammonium readily.. happily.. and its much less toxic to fish at the lower ph


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## Rockhoe14er (Jan 19, 2011)

I have no idea if my bacteria are working or not but my pH is at 5.4 and my heavily stocked fish tank is doing just fine. I measured my ammonia and nitrite and got zero's across the board. My pH only gets to around 6 at night. The fish seem to be just fine and nice and healthy.


it would be interesting if my wasn't planted to see if i got get a colony of bb that could digest ammonia at lower pH levels.


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## bsmith (Jan 8, 2007)

Rockhoe14er said:


> I have no idea if my bacteria are working or not but my pH is at 5.4 and my heavily stocked fish tank is doing just fine. I measured my ammonia and nitrite and got zero's across the board. My pH only gets to around 6 at night. The fish seem to be just fine and nice and healthy.
> 
> 
> it would be interesting if my wasn't planted to see if i got get a colony of bb that could digest ammonia at lower pH levels.


Do you ever get Green Water outbreaks?


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## 150EH (Dec 6, 2004)

I think we all need to do a little calibrating on the test kits, that's why I even bother to test anymore. But my water starts to get a white haze with too much C02 just before fish death, is it from bacteria shutting down, not sure but my tank functions better at a good or reasonable level and takes a dive at high levels of C02. 

At some point the water has to become too acidic, but even the caustic acidic waters at Yellowstone have bacteria but I'm sure it's not related to anything in my filter.

My pH is 7.4 out of my tap, 7.2 in the tank and I don't know how it drops by just going into the tank, my plants grow nice with a pH of 6.8 or 6.6, but below that I get the white haze and dead fish are next and it's with a pH of 6.4 or so.

But test kits are so unreliable I use mine to hold my DIY bubble counter off the floor since I upgraded to a 10# C02 tank and didn't feel like putting in some new line, that's how good test kits are.


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## Rockhoe14er (Jan 19, 2011)

bsmith said:


> Do you ever get Green Water outbreaks?


actually no, as of right now my water is crystal clear. Sometimes my water looks a bit like a can of 7 up because of how much co2 i pump in.

Also i have a pH probe that I calibrate every two weeks so i'm pretty sure my reading is accurate.


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## bsmith (Jan 8, 2007)

Rockhoe14er said:


> actually no, as of right now my water is crystal clear. Sometimes my water looks a bit like a can of 7 up because of how much co2 i pump in.
> 
> Also i have a pH probe that I calibrate every two weeks so i'm pretty sure my reading is accurate.


Oh my water is super clear aswell but I get GW from time to time after WC's. I believe it was when I cleaned the biomedia in my canister with tap water. Perhaps that killed just enough of the bacteria to cause a waterfall effect with bacteria die off causing an ammobis spike then causing the GW.


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## willknowitall (Oct 3, 2010)

Hoppy said:


> People use lots of CO2 with high light tanks. That must necessarily drive the pH down almost always below 6.5. Those people find they have much less algae problems than if they don't use the CO2, and I would expect the opposite if the low pH was doing significant harm to nitrifying bacteria. Of course, it is always recommended to shut off the CO2 when the lights are off, which should be for about 14-16 hours a day, so any harm to the bacteria may be reversed during that time each day.


i have been reading studies that show nitrifying bacteria are sensitive to low ph but are extremely sensitive to ph fluctuations including ph changes from co2
which to me suggests keeping a constant co2 level 24 /7


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## Rockhoe14er (Jan 19, 2011)

after water changes i haven't seen any green water so far but i've only had the tank set up here for about a 2 months so who knows. 


I disagree about keeping the co2 on 24/7 because i know i wouldn't be able to keep my levels as high if they were on 24/7 and also i have zero ammonia and nitrites even with the co2 fluctuation. I guess as long as you have good plant growth it shouldn't matter.


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## bsmith (Jan 8, 2007)

Do you have any source that shows they specifically do not like pH fluctuations from Co2? The only reason I ask is because pH fluctuations from co2 are kind of fake. I could be wrong but its like the pH really doesn't fluctuate because there is nothing being removed fro the water.


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## willknowitall (Oct 3, 2010)

Rockhoe14er said:


> after water changes i haven't seen any green water so far but i've only had the tank set up here for about a 2 months so who knows.
> 
> 
> I disagree about keeping the co2 on 24/7 because i know i wouldn't be able to keep my levels as high if they were on 24/7 and also i have zero ammonia and nitrites even with the co2 fluctuation. I guess as long as you have good plant growth it shouldn't matter.


if you had a ph controller you would be able to keep the co2 levels as high as you have been and i might add more consistant through out the day


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## bsmith (Jan 8, 2007)

Rockhoe14er said:


> after water changes i haven't seen any green water so far but i've only had the tank set up here for about a 2 months so who knows.
> 
> 
> I disagree about keeping the co2 on 24/7 because i know i wouldn't be able to keep my levels as high if they were on 24/7 and also i have zero ammonia and nitrites even with the co2 fluctuation. I guess as long as you have good plant growth it shouldn't matter.


Yeah im with you on this one. I think that keeping the gas on 24/7 would asphyxiate the bacteria and that would pose more of an issue than the fluctuating pH.


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## Rockhoe14er (Jan 19, 2011)

willknowitall said:


> i have been reading studies that show nitrifying bacteria are extremely sensitive to ph fluctuations including ph changes from co2
> which to me suggests keeping a constant co2 level 24 /7


I also feel if this were true nobody with pressurized co2 would be able to have nitrifying bacteria because co2 causes the pH to change a lot.


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## willknowitall (Oct 3, 2010)

Rockhoe14er said:


> I also feel if this were true nobody with pressurized co2 would be able to have nitrifying bacteria because co2 causes the pH to change a lot.


well first off . there are many degrees of health of the Bactria , as in, ok there sort of holding out , or there thriving
secondly who here has a high powered microscope to actually gauge there populations
a lastly ..hahaha ok im looking for link


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## willknowitall (Oct 3, 2010)

hi i found a lot of links suggesting bacteria sensitive to ph change but not the one on specifically ph change from co2 but still looking 
heres a interesting link i found on nitrifying bacteria though, which explains why low bacteria and low ph doesn't effect fish 
and i might add why co2 fluctuations dont kill bacteria but just stop them from functioning and reproducing and why consistent co2 ok
http://www.oscarfish.com/article-home/water/71-autotrophic-bacteria-manifesto.html


also as i side note here , my water has been much clearer when i run co2 24/7 then when i have shut it off at night


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