# calculating co2 levels KH 17.8



## James Flexton (4 Sep 2014)

Hi All,

im trying to work out the level of co2 in my tank. however the water here is very hard.

ive been in touch with the water company and they said the water is KH 17.8. so on that basis im aiming for a PH of around 7.2 to have 25ppm co2.

however when my test kit (so shoot me down in flames ceg!) indicates around 7 ish the drop checker with 4KH water in it is blue rather than green.

in order to get a green drop checker i have to pump in around 5 bubbles per second to the inline diffuser and in that instance the PH is reading around 6.3 however looking at a co2 chart with my KH being so high at a PH of 6.3 im at around the 200/250ppm co2 level which is 10 times what im aiming for.

so seeing as both measurements (drop checker and api test kit) are basically the devil incarnate test kits then which is wrong. 

and i know trial and error is the answer and let the plants tell me however i dont want to poison the fish when i put them in the tank further down the line if in 10x the co2 i need to be.

help please, im going round in circles..
 (tank is in the journals section - "twin peaks")
cheers


----------



## ian_m (4 Sep 2014)

Drop checker is more accurate as consists of 4dKH water, indicator and CO2. No other tank chemicals, EI salts, silly expensive test kits and water company results etc etc to interfere with result. If green heading yellow, then you are good to regardless what your hopelessly incorrect test kit says.


----------



## parotet (4 Sep 2014)

Hi James, glad to know another member that fills his planted tank with liquid rock... PH 7ish, KH 15+, GH 21+, scale buildup in one day... What a wonderful world!

Well my experience is that I have only achieved a PH drop of 1. As Ian says don't pay attention to the chart which is obviously not giving any useful information. Definitely you do not have 250 ppm of CO2 in your tank,you should be happy if you will achieve something around 25 ppm. Focus on having a nice lime green at lights on (in my case I have to switch on the co2 3 hours before light and when the tank is crowded I inject 4 bps through an atomizer... In just 65 liters). Pay also attention to homogeneous and effective flow to keep fish in good condition as well as good aireation (rippling with a spraybar, letting your lily pipe outlet a bit higher at night, using a sump...) and.... Let it grow, your plants will tell you if everything is ok. 

Jordi


----------



## James Flexton (4 Sep 2014)

thanks guys. there are no ei salts or anything in there tanks just set up.
im ignoring test kit results at the moment as i know im not getting 250ppm co2 its just thats what the readings correlate to. i know they are innacurate but didnt realise they are totally pointless

ill leave it as it is for now and let it grow. there are no fish currently so no issue with overdosing. not that i think i could anyway with my water.


----------



## ian_m (4 Sep 2014)

The test kits perform an excellent function of transferring money from your wallet to the retailer. The test kit results then encourage you to transfer even more money correcting the results from the test kit.


----------



## John P Coates (6 Sep 2014)

James Flexton said:


> Hi All,
> 
> im trying to work out the level of co2 in my tank. however the water here is very hard.
> 
> ive been in touch with the water company and they said the water is KH 17.8. so on that basis im aiming for a PH of around 7.2 to have 25ppm co2.


Hi James,

I'm trying to understand what you have said above. Does your tap water really have that much carbonate hardness? If so, what is the general hardness (GH)? Is it possible that there is an error here? I say this because 1 unit dH is equal to 17.8ppm of calcium carbonate. The important thing here is the figure of 17.8. Do you get my drift? Would it be possible to check again with your water company the carbonate hardness figure in either °KH or calcium carbonate equivalent in ppm? Alternatively, measure the KH yourself with a test kit. The Salifert test kit is favoured by many but I have used NTL and Nutrafin with no problems.

JPC


----------



## James Flexton (6 Sep 2014)

John P Coates said:


> Hi James,
> 
> I'm trying to understand what you have said above. Does your tap water really have that much carbonate hardness? If so, what is the general hardness (GH)? Is it possible that there is an error here? I say this because 1 unit dH is equal to 17.8ppm of calcium carbonate. The important thing here is the figure of 17.8. Do you get my drift? Would it be possible to check again with your water company the carbonate hardness figure in either °KH or calcium carbonate equivalent in ppm? Alternatively, measure the KH yourself with a test kit. The Salifert test kit is favoured by many but I have used NTL and Nutrafin with no problems.
> 
> JPC



Hi John. The water company initially said the KH is 320. Which threw me as I was expecting something on the 1-20 scale. They then converted it and came back with 17.8. The guy in their testing lab that I spoke to said 320 (I don't know what that is measured in) is the top level of hardness that it can be. Areas in their terms are very soft, soft, hard, very hard etc. I'm not surprised it came back at 17.8 as I have a crusty water line from evaporation every 3-5 days or so and kettles get totally furred up in a month or two. I'm in Hertfordshire which is a hard water area. The ph I mentioned above is what I'd need assuming my KH is 17.8 going by a co2 chart. 

I haven't got a KH test kit but thought the water company data would be more accurate to go on. 


Sent from my iPhone using Tapatalk


----------



## John P Coates (6 Sep 2014)

James Flexton said:


> Hi John. The water company initially said the KH is 320. Which threw me as I was expecting something on the 1-20 scale. They then converted it and came back with 17.8. The guy in their testing lab that I spoke to said 320 (I don't know what that is measured in) is the top level of hardness that it can be. Areas in their terms are very soft, soft, hard, very hard etc. I'm not surprised it came back at 17.8 as I have a crusty water line from evaporation every 3-5 days or so and kettles get totally furred up in a month or two. I'm in Hertfordshire which is a hard water area. The ph I mentioned above is what I'd need assuming my KH is 17.8 going by a co2 chart.
> 
> I haven't got a KH test kit but thought the water company data would be more accurate to go on.
> 
> ...


Hi James,

OK, that's cleared that one up. The figure that you were first given would be 320 ppm calcium carbonate equivalent. As it happens, if you divide this figure by 17.848, you end up with 17.929. That's why I thought the figures may have got mixed up. It seemed too coincidental that the figure of 17.8 you quoted in your first post also happened to be the conversion factor (give or take a gnat's whisker) for converting from ppm to °KH.

So, yes, it does look as though you have a whopping 320 ppm KH in your tank and that does equate to 17.9 °KH. I am uncomfortable working at such high levels of water hardness. Do you also have fish in your tank and, if so, what do you have? Please also ask your water company what the GH is. I'd be tempted to use RO water to which you can then add salts thus bringing your water parameters to more manageable levels.

It's getting late now and my brain is flagging but I hope to give this interesting problem more thought tomorrow morning.

JPC


----------



## James Flexton (7 Sep 2014)

John P Coates said:


> Hi James,
> 
> OK, that's cleared that one up. The figure that you were first given would be 320 ppm calcium carbonate equivalent. As it happens, if you divide this figure by 17.848, you end up with 17.929. That's why I thought the figures may have got mixed up. It seemed too coincidental that the figure of 17.8 you quoted in your first post also happened to be the conversion factor (give or take a gnat's whisker) for converting from ppm to °KH.
> 
> ...



No fish in the tank yet but I have had numerous tanks for the past 10 years. At present the only other tropical tank I have up and running is a 100 gallon low tech semi planted tank with South American cichlids and 15 sterbai cory's. I've successfully kept high tech planted tanks in the past from around 2004-2009. Then left the hobby due to work commitments. You may have seen the articles on plant maintenance and the step by step riccia article on here. Plenty of pics of my tanks there. I didn't realise at the time but I did have very good plant growth using both DIY and pressurised co2 which theoretically should be pretty easy given such hard water. I've always avoided RO as with dosing ei and big water changes it's too much hassle. 

As to fish I've kept angels cardinals cory's all lived many years in seemingly good health. Rams always died in a few weeks and I also had an African cichlid tank for about 4 years. 

I'll run this tank on the local tap water and see how it goes. I'm confident it will be ok. Might run fish stocking options by you lot first though. I was thinking of shrimp. But not sure how they fare in such hard water. 

Thanks for taking an interest in the thread john. 


Sent from my iPhone using Tapatalk


----------



## ceg4048 (7 Sep 2014)

James Flexton said:


> in order to get a green drop checker i have to pump in around 5 bubbles per second to the inline diffuser and in that instance the PH is reading around 6.3 however looking at a co2 chart with my KH being so high at a PH of 6.3 im at around the 200/250ppm co2 level which is 10 times what im aiming for.


For the 1,000,001th time you cannot use the charts to tell you how much CO2 is in the tank.
With an alkalinity of 18 just aim for a 0.5 pH unit drop from gas on to lights on.
You are wasting precious time worrying about dissolving CO2 in high KH water. There is no relationship between the alkalinity of the water and the ability to dissolve CO2 in that water. Gas solubility has nothing to do with alkalinity.
You simply don't have a high enough injection rate, or your dissolution/distribution methods are poor, or all of the above.

Cheers,


----------



## James Flexton (7 Sep 2014)

ceg4048 said:


> For the 1,000,001th time you cannot use the charts to tell you how much CO2 is in the tank.
> With an alkalinity of 18 just aim for a 0.5 pH unit drop from gas on to lights on.
> You are wasting tie time worrying about dissolving CO2 in high KH water. There is no relationship between the alkalinity of the water and the ability to dissolve CO2 in that water. Gas solubility has nothing to do with alkalinity.
> You simply don't have a high enough injection rate, or your dissolution/distribution methods are poor, or all of the above.
> ...



Thanks ceg,

Well at 4 bubbles per second I drop about 0.5 ph in 2 hours however at that point the drop checker is still green. And I mean an emerald green not lime green.. His is why I was concerned as I see a lot on here with almost yellow drop checkers, distribution is fine. Reading is the same wherever in the tank I place the drop checker. 


Sent from my iPad using Tapatalk


----------



## John P Coates (7 Sep 2014)

ceg4048 said:


> For the 1,000,001th time you cannot use the charts to tell you how much CO2 is in the tank.


Is this statement completely correct? Under some circumstances, it can give a good approximation as you indicated to me recently. See the edits below.

One of the reasons, I still use the chart is because I often want to get an idea of dissolved CO2 concentration at a particular point in time. Plus, the anions in my water are indeed primarily carbonates. Because of the inherently slow-to-respond nature of the drop checker, using the chart is my only option.

JPC

EDIT:  "The charts are a very rough guide because they assume that the KH of the water is due to Carbonates - and that's not really true for most tap water". I don't use tap water. Instead, I use RO to which I add minerals.

"If you want to use this chart, and if the KH is 100% due to Carbonate then use the values a couple of blocks into the red zone. That more or less will come closer to accounting for the acid discrepancy and more or less will accomplish the same as the pH profile method...".


----------



## dw1305 (7 Sep 2014)

Hi all, 
The "320" is 320 ppm (or mg/l, they are equivalents). The dGH will be similar to the dKH, because the aquifer is chalk, which is pretty pure CaCO3, you should be able to get a value for calcium from the water company. The workings are here for our tap water (from a limestone aquifer) <"How do I work out ......">, also worth having a look at <"All about water hardness">.  Once the water is out of the water main, and has warmed and de-pressurized, it will precipitate CaCO3 (you can often see this as "milkiness" in a glass of water). This means that you can't get the pH above ~pH8 where carbonates are the source of the hardness. This is to do with the solubility of CaCO3 (it isn't very soluble), and at ~pH8 your solution is saturated with Ca++ and HCO3- ions, and this is why slight changes in water temperature, or  water volume (via evaporation), will lead to CaCO3 precipitating out as "scale".  If you add a soluble carbonate salt like NaHCO3 to the solution you will get also get CaCO3  precipitated, this is due to the "common ion" effect. 

Calcium carbonate is technically insoluble, but when CO2 dissolves (including the 400ppm in the atmosphere) it becomes soluble (details here "Calcium bicarbonate"). You can't infer the level of CO2 based upon the pH and dKH, but you can use the 4dK drop checker solution (because all HCO3- ions in solution) and pH to estimate the CO2 level. I hope that makes more sense now.

cheers Darrel


----------



## ceg4048 (7 Sep 2014)

Exactly. Also, even if it was the case on an individual basis, it's a very bad idea generally to assume that all the alkalinity in the water supply is 100% Carbonates. That's why using the charts blindly results in failure most of the time.




James Flexton said:


> Well at 4 bubbles per second I drop about 0.5 ph in 2 hours however at that point the drop checker is still green.


OK, that's being on the right path. However, as I mention often, a green dropchecker doesn't guarantee anything because how much CO2 you need in the water for your plants under your conditions may or may not equate to that particular color. There are many with a yellow DC and everything is fine. There ore others with a green DC who continue to have problems. Maybe, in your case, a 0.6 or 0.7 unit drop is needed. I can't predict the answer to that. I gave you general numbers, but if the plants fail with that number you must be prepared to use a a larger number if the fish are not experiencing difficulty. 

Cheers,


----------



## James Flexton (7 Sep 2014)

ceg4048 said:


> Exactly. Also, even if it was the case on an individual basis, it's a very bad idea generally to assume that all the alkalinity in the water supply is 100% Carbonates. That's why using the charts blindly results in failure most of the time.
> 
> 
> 
> ...



Ok thanks ceg that makes sense. I'll carry on as I am then for a few weeks and observe the plants. If there are signs of low co2 I'll up the bubble rate. I think I was falling for the trap of getting too hung up on the readings. As a rule of thumb though what would be useful to know is if my co2 input is too high for fish health (bearing in mind tank is plant only currently) is it actually the co2 content that is bad for the fish or the resulting ph drop. Calculating ph is easy but co2 content less so. 

If I can get the tank to the optimum co2 level for the plants, then test ph. If ph is within fish health margins then will I be ok to stock the tank without having to worry about high co2?


Sent from my iPhone using Tapatalk


----------



## ceg4048 (7 Sep 2014)

James Flexton said:


> As a rule of thumb though what would be useful to know is if my co2 input is too high for fish health


Yes, I agree. That is what the DC is supposed to help you with. That is also what the ph drop general number is based on as well. If the DC is green then generally, you should be OK. If the ph drop is held close to these numbers then is should be OK for fish and good for plants. Try stocking first with a few inexpensive fish first and add them pre CO2 gas on time on a day when you will be home to observe. It's very easy to fix the problem if you observe the fish in discomfort. 

Cheers,


----------



## James Flexton (7 Sep 2014)

ceg4048 said:


> Yes, I agree. That is what the DC is supposed to help you with. That is also what the ph drop general number is based on as well. If the DC is green then generally, you should be OK. If the ph drop is held close to these numbers then is should be OK for fish and good for plants. Try stocking first with a few inexpensive fish first and add them pre CO2 gas on time on a day when you will be home to observe. It's very easy to fix the problem if you observe the fish in discomfort.
> 
> Cheers,



Ok will do. 
Sorry to labor the same question but if fish are in discomfort is it because of the co2 directly or the resulting ph drop?


Sent from my iPad using Tapatalk


----------



## ceg4048 (7 Sep 2014)

Oh, golly, sorry mate, I zoned out after inadvertently voting for "favorite test kit". 

In any case, fish do not really care about pH. Check these threads:
http://ukaps.org/forum/threads/what...h-co2-or-dramatic-ph-swing.26660/#post-277056

http://www.ukaps.org/forum/threads/not-enough-oxygen.14774/

Cheers,


----------



## Andy D (7 Sep 2014)

I have copied this from one of Clive's posts:

"The toxicity of CO2 has to do with the dissolved gas pressure in the water which makes it difficult for the fish to exhale. Imagine if I put a plastic bag over your head and forced you to re-breathe the air you exhale. Any living thing that consumes carbohydrates, and which burn the carbohydrates with Oxygen will always produce CO2 which has to be eliminated from their system. Within the bloodstream, the Carbonic acid that results from the tissue produced CO2 changes the pH of the blood and that acidity inhibits the Oxygen carrying ability of red blood cells. We and fish have to expel the CO2 or suffer hypoxia. High CO2 pressure in the water column pushes back against the fishes attempt to push CO2 out through the gills."

EDIT - although he has answered now.


----------



## James Flexton (7 Sep 2014)

Thanks guys that's great. I'll keep you posted on how things go over the next few weeks. Cheers for the input


Sent from my iPhone using Tapatalk


----------



## Andy Thurston (7 Sep 2014)

> Imagine if I put a plastic bag over your head and forced you to re-breathe the air you exhale


I've seen this bit a couple of times and now i  every time i read it
Sorry


----------

