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Adding CO2 to a Tank with a pH of 6

Bobtastic

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13 May 2009
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745
Location
Manchester, UK
Hi all,

I'm toying with the idea of adding pressurised CO2 to my new 240L tank that I'm gonna start planting soon, but the pH of the water from the tap is only 6... I'm a bit concerned that if I add CO2 it's gonna drag it down, this could harm the fish I eventually put in or stop the bacteria from even growing...

Any one had experience with this?
 

JamesC

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3 Jul 2007
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Location
Bexley, Kent
Put some tap water in a glass and leave 24 hours and then measure the pH again. It may already contain some CO2 which is why your tap pH is quite low.

I take it your tap water is very soft. If it is and you are concerned about the low pH then just add a bit of potassium carbonate or baking soda at each water change. Personally I wouldn't worry too much about it and adding chemicals to adjust the water parameters only complicates things. Many people run high CO2 with zero KH and don't seem to have any problems. I've run my tank down to about a pH of 5.5 with no ill effect.

Anyway let us know what the pH of the water in the glass is.

James
 

zig

Member
Joined
4 Jul 2007
Messages
686
Location
Dublin Ireland
Are you sure the pH kit is ok, is it in date and what make is it, its not those strips by any chance? I would say its possibly wrong, I could be wrong as well mind you, Im no expert. But I would expect your GH/KH to be practically zero for the pH to be reading 6. Your GH is 2.24 degree dH and your KH 1.68 degree dh, low, but not particularily low IMO, its around the same as mine and my pH reads 7 before I add CO2, when I add CO2 it drops to 6 pH or thereabouts.
 

ceg4048

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11 Jul 2007
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Chicago, USA
Bobtastic said:
Ok tested the water again, that's gotta be at least 72hrs and the pH is still reading 6. I also tested the GH/KH, GH comes back as 40 mg/l and KH comes back as 30 mg/l.
Opinions?
Yeah, just stop worrying about it.

The concern you expressed:
Bobtastic said:
..if I add CO2 it's gonna drag it down, this could harm the fish I eventually put in or stop the bacteria from even growing...
is completely unfounded. About the only way you'll stop bacteria from growing is if you dump a couple liters of bleach in there every week.

Assuming you keep South American species such as neons or angels, the freshwater systems that your fish are native to vary in pH from a high of about 6.5 to a low of about 4.5 (sometime even lower in the blackwater systems): Blackwater/Whitewater comparisons
Excerpt: Cichlid fishes: behaviour, ecology and evolution

If you're concerned with the GH then just ad a few teaspoons of GH Booster once a week and if you're concerned about KH then just buffer it with some Potassium Carbonate

Cheers,
 

Fred Dulley

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8 Jul 2007
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558
Location
Cardiff, Wales
Bobtastic said:
Ok, I seem to get conflicting advise/information everywhere I go! :crazy:


Because they're still plugged into the Matrix and reiterate false claims to other people when they hear them. Just like "nitrates and phosphates cause algae".
Good luck Bob.
 

Bobtastic

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Thread starter
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13 May 2009
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Manchester, UK
I was wondering what sort of affect the drop in pH from 6 due to to pressurised CO2 would have on the below plants :-

Hydrocotyle verticillata

Cryptocoryne beckettii

Lilaeopsis brasiliensis

Hemianthus callitrichoides "Cuba"

Cryptocoryne wendtii 'Green'

Cryptocoryne wendtii 'Brown'
 

Anita

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5 Apr 2009
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12
Location
Plymouth, Devon UK
I also have a pH of around 6ish, my kH out of the tap is 0. I also have pressurized CO2.
I've kept discus for years and always used a little coral gravel in one of the filters.
I like it because it's slow working, wait a couple of weeks and if you see the pH going a bit high reduce the amount of gravel. Not high enough add a little more. It lasts a good while too, around 6-8 months you may notice the pH dropping (will happen slowly) this is because the acidity in your water has reduced the amount of gravel that you originally added, so a top up will be needed.
 

howanic

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28 Jul 2008
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London
Try not to worry so much about it. As long as your ph does not fluctuate wildly you have nothing to worry about. I have used straight ro water to get my rams to breed with co2 without problems. Just make any adjustments slowly and you will be fine
 

CeeJay

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3 May 2009
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Surrey UK
Hi all
howanic said:
Try not to worry so much about it.
Couldn't agree more.
I learnt a while ago from plantbrain that pH adjusted by adding CO2 does not stress the fish half as much as a pH that's been adjusted using salts. Can't remember the title of the post but I'll have a search and post it up if I find it.
Just one less thing to worry about :D .

Chris
 

Dave Spencer

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Bob,

You talk about conflicting advice, but is there conflicting evidence? Some forums love to talk about pH "crashes", and how you need to buffer this, that and the other, but none of these persons speak from experience. A lot of them could easily prove to themselves that you can inject CO2 in negligible KH, but the overwhelming advice seems to be to raise the KH to an arbitrary figure of 4. o_O I can guess where you are getting your advice from on other forums, and they are wrong to give this advice.

There is currently a thread on another forum where a woman has Angels and breeding Corys in lovely soft water with a pH 6. However, she is not happy with the pH and wants to alter the kH. HELLO! The water is there to keep the fish happy, not satisfy her woeful knowledge of water chemistry. To be fair, it probably isn`t her fault, considering the terrible advice she will have been reading on a daily basis.

I have soft water, with all manner of processes driving the pH down to who knows where. My fish seem happy, as do my filter colonies.

pH drops due to CO2 and pH "crashes" are among the most overplayed cards out there.

Dave.
 

George Farmer

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Indeed, pH crashes are often deliberately brought about to induce spawning in some fish, but these are not brought about by CO2....

I know of plenty of planted tank owners that run KH 0 with no issues long-term.

Simply concentrating more on regular maintenance, such as water changes, filter cleaning, pruning, CO2 and nutrient control, and these will give better results than any alterations to water chemistry.
 

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