A Question Of KH

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adrianhaslett
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A Question Of KH

Post by adrianhaslett »

After buying my RO Unit i'm trying to get the water softer for my Zebra and later other soft water fish.

I've been experimenting with mixes of RO to Tap water (Don't worry not in the tank). From reading I have relized that I want a PH os somewhere between 6.5 to 7.5 and a good buffering capacity (KH) so it stays there.

MY test kit a hagen Liquid one is the same as most you changes the colour from blue to yellow after adding drops and then you convert it to mg/l by mutiplying by 10 if I do a 3/4 RO to 1/4 Tap I get a PH of 7 and a KH mg/l of 30 but am I right in saying that this KH is way to low, I read to convert it to dH I mutiply by 0.056 which gives 1.68 and I think i'm looking for a minumum of 4 dH am I right ?. I am testing this using a 20 ml cap and adding 3 RO to one tap and mixing is this right ?.

Any help would be great my original plan was to add straight RO to the tank gradually weekly until I get the right KH and PH and then keep it there my the RO/Tap mixes.
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Andrew C
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Post by Andrew C »

Adrian
How many drops dos it take to turn the test tube yellow ?

Using the amount of drops, 3 or 4 drops before the test tube turns yellow is minimal buffering and will stop any ph swings, and you can use the amount of drops to turn the test tube yellow as scale, and say you have a KH of 3 or 4 (my Aquarium Pharmicuticals test kit dos this).

The water out of my tap turns yellow on the first drop, a KH of 1, it is very soft and i add bi-carbonate of soda to my tap water to get some buffering in it for my general tropical fish, but for softer water fish i don't bother adding bi-carb, as softer water fish are used to a low KH (it goes with softer water) and can handle small ph swings as they are more used to it.
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Post by ivanpantz »

Hello.

And don't forget one thing. By adding NaHCO3 (bi-carb) you'll also be raising the pH of the water, because NaHCO3 is a base.

Most people think that KH (Carbonates and Bicarbonates) are the only water buffers. This is not true... For exemple, peat lowers KH, pH and GH, and that doesn't mean that the water's pH is unstable. A buffer solution is made by dissolving an acid and a conjugated base of that acid... depending on the pKa of the acid, the pH that the buffer maintains is more or less acid.

And peat mantains the pH low and stable. But as you well know, it also darkens the water because of the tannins.
Any help would be great my original plan was to add straight RO to the tank gradually weekly until I get the right KH and PH and then keep it there my the RO/Tap mixes.
You can do that, but it will become a problem after you level the pH and KH you want... then what water will you use? Unless you also start to test mixing RO water with tap water to obtain a proper pH and KH, it will be difficult to maintain them in the aquarium.
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Post by adrianhaslett »

That KH bit is where I get so confused, on sites you see it say Hardness 4 or above which seems great so as you say my test kit takes 3 drops to turn yellow all was o.k then I read further and it said to convert this to mg/l multiple by 10 and other sums you can do but nowwhere does it say about what the standreded 3 drops without any calculations mean. On the hagen website it has a convertor if you type in 30 mg/l which is derived from the sum it gives you it says this is:

1.680 DH
2.10 Clark H
3.0 fH
30 Hardness
0.60 mEq/L

see what I mean confusing as hell. As I say when looking at the minumum buffereing capacity for aquarium fish it says at least 4 but it does not say what 4.

If my dops on the hagen are the same as other tests mentioned here and 4 just means 4 drops untill turns yellow than that's cool. But I want to be certain because ovouisly I don't want to little buffering capacity because of big PH swings.

And as pointed out when I get down my tank to the required water requirments then I have to add water during water changes a mix of RO and Tap. I've worked out that doing a 3/4 RO to 1/4 tap will give me a PH of 7.0 and KH of 3 but this still might give a ph swing when adding to existing PH of the same level because I've read you don't have to premix before adding to tank you could just put in the equivalant to 3/4 ro and then addd the 1/4 tap plus declroinator because of the tap water but who's to say how this will affect the existing water of the same chemistry. For example when I add the RO it will graetly decraese the ammount of KH for a while untill I add the Tap and this may cause or other factors a PH swing. Not having used RO before I now the theory roughly but have never done the mixing bit into the tank so don't know if this does cause PH differences regularily. Someone might be able to answer this ?
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Post by AndyAps.com »

you can go on the drops before the solution turns colour.
as you only times by 10 to get your result then 3 is the same as 30, 4 is 40 etc.
my nutrafin GH/KH test kit has this on back of the instructions

KH- Multiply the number of drops by 10 to determine carbonate hardness in MG/L
<20 mg/l - Adjust with appropriate buffer if needed
20-80mg/l - normally associated with a low PH (good for fish that prefer acidic PH)
>80mg/l - Excellent buffering capacity but associated with high PH

Conversion table
Multiply GH or KH mg/l by the following
x1 = hardness degree
x0.02 = mEq/l
x0.056= DHdegree
x0.07 = Clark Hdegree
x0.01= FHdegree

Hope that helps
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Post by Raul-7 »

kH is commonly measure in both dKH and meq/L. Ignore the other figures - concentrate on the .60 meq/L and 30 ppm (mg/L = ppm). They all mean the same thing, just different units of measure. 1 meq/L = 2.8 dKH = 50 ppm CaCO3 equivalents. Thus you have a carbonate hardness of 1.7 dKH, aim for at least 3 dKH.

As for doing water changes, etc. everyone I know who uses RO and tap premixes them before adding them to the aquarium. They use a large 33G canister, add the correct RO:Tap ratio and add it from there. You don't want to mix them in the aquarium itself, too large of a change will occur.
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Post by adrianhaslett »

Thanks for the info, I went down my local LFS because things are looking weird after 2 pure RO water changes of 20 Gallons each i.e 40 Gallons in total for a 6'2'2 with double base and a few inches from the top makes about 120 Gallons of water I have the following measurments

KH 6
GH 8
PH 8.0

See what I mean weird the Hardness is going down to good soft water perimeters but the PH remains high. After speaking with them they said the same thing happens arround there LFS you can get low hardness i.e soft warter but the PH will remain at 8.0 if just using RO and Tap water Combo's. They said they have to use PH down ACid Buffers to get the water down to 6.5-6.8.

I got ever so confused. They also said instead of using RO-Tap use RO-RO Waste, the RO waste is better than Tap water but worse than pure RO and is Chloriine free because it's gone through the carbon filter. ?.

Anyway went away with some JBL Catfish Pellets and some Tetra Prima both which the Zebra Plec does not seem interested in, he only likes Bloodworm so far but i'm worried the Nutrition won't be anough on Bloodworm alone ?.

All this fuss for one L046 EH!
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Post by ivanpantz »

Hello again.
adrianhaslett wrote:See what I mean weird the Hardness is going down to good soft water perimeters but the PH remains high.
Nop... that's normal...

You see, RO water has a buffer capacity of 0... this means that even if you mix a little bit of acid, or basic water, the pH of the RO water will change drasticaly.

By adding RO water to your tank, it will lower the KH and GH, but the pH will remain the same.

My regards.
Luís Fortunato
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Post by adrianhaslett »

So it looks like more money, What do i need and how easy is it to regulate at that PH with frequent water changes i.e are you saying it's best not to use Tap water and use RO Right to get to the correct PH etc for water changes and use a product acid buffer to get the existing water in the tank to arround 7.0.

The hole idea was even though the RO was expensive to buy to use this with some tap to get ideal conditions. But it seems it's more complicated and I don't want to stress out the fish.

As I say by raeding it seems i will have to buy a acid buffer like Kent Acid Buffer to drop the existing tank Ph at least. And perhaps some RO Right to get good acid water during water changes without tap water.

Sorry about the constant questions but I see alot of discussions everywhere about using RO but none about thisbit of using RO.
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Post by Andrew C »

RO Water is pure water and if added to a tank of water with the readings you stated, it will dilute the kh and gh, which should lower the ph.

It is the kh (buffering capacity) of the water that keeps the ph stable and if it is diluted, the ph should lower.

I hope you are trying these tests on a water storage tank and not on a tank that has fish in it ?

Adrian,
If you are finding it hard to understand water chemistry, keep using your tap water and read up on water chemistry, as well as trying your experiments on a water storage tank without any fish in it, as getting too many oponions will have you going around in circles.

http://faq.thekrib.com/begin-chem.html
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Post by adrianhaslett »

No don't worry all tests are being done in glasses, I have a 20ml cap I decide what I want to do i.e 1/4 tap to 3/3 RO and then do this by taking the ro from the storage tank and then the tap. I only have a 2ft tank i'm using for the RO storage at present that takes 15 Gallons of water which is o.k at present if I do this type of mix doing 20 gallon water changes.

THe only issue is that I take the RO water direct from the storage tank that is not airated or anything it just sits in the 2ft tank and then add the tap water to the glass and stir and take a measurment. Should I be airating the RO in the storage tank or does it not matter. I will also have a look at that website you mentioned.

What about the food for my zebra he only eats bloodworm, i bought tetra prima and catfish pellets but no go ?.
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Post by ivanpantz »

Hello again.
Andrew C wrote:RO Water is pure water and if added to a tank of water with the readings you stated, it will dilute the kh and gh, which should lower the ph.
Not really pure water. Close, but not pure... pure water would be distilled water.

Although KH and GH are related to pH, that's in non-chemically manipulated water.
As you can see, from adrianhaslett post, even if you dillute KH and GH in your water, unless the change is too big, the pH drop will not occur.
For example, if you take a gallon of RO water, and add a little bit, say 250 ml of a aquarium water with a pH of 8.0, the pH of the final solution will not be very different from 8.0. Because the RO water has no buffer capacity... and the final pH will be exclusively dependent of the pH of the aquarium water.
adrianhaslett wrote:Sorry about the constant questions but I see alot of discussions everywhere about using RO but none about thisbit of using RO.
Feel free to ask what you want... this is a Forum. Its essence is to share information and knowledge...

Nowadays, people take more interest in GH and water conductivity than pH itself. Of course they're related (pH, KH and GH)... but in natural systems. We're talking about chemical-manipulated water. And that makes all the difference.
For example, if you dillute CO2 in water, the KH will rise, and the pH will drop.

I don't know if you have ever tried peat. Yes, the water will turn brown/yellow, but peat will lower pH, as well as GH and KH.

RO water is good in turning the KH and GH low, as well as the conductivity. And for south-american fishes, is good to hatching eggs because of the osmotic effects. The softer the water, the less probably an egg will become infertile (i don't know if this is the right term).

There's a post in this Forum talking about water conductivity, and the effect on zebra spawning:

http://www.zebrapleco.com/forum/viewtopic.php?t=2076

The link Andrew C provided is a good start to know about water chemistry.
Read it, and if you have any doubts, fell free to ask...

My regards.
Luís Fortunato
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Post by adrianhaslett »

Any advice on the food part, as I say getting worried that bloodworm all the time is not anough nutrition. Might get the wife to mix up some of that mceve recipe I saw somewhere.

I beginning to think should have left well out of the RO business and kept with normal tap water changes but better not tell the wife after spending all that money !.

Or go marine it seems the tap water arround here is better suited to marine add a bit of salt and heh presto some yellow tangs appear.
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Post by discusbabe »

I did try and warn you about RO! :P
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Post by Raul-7 »

ivanpantz wrote: For example, if you dillute CO2 in water, the KH will rise, and the pH will drop.

My regards.
Luís Fortunato
When you dilute CO2 into the water, the pH will drop but the kH will remain constant. That's how we are able to measure CO2 concentrations using the kH-pH relationship. :wink:
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