RO water's ph.. make difference? - The Planted Tank Forum
 
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post #1 of 14 (permalink) Old 05-05-2008, 02:37 PM Thread Starter
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RO water's ph.. make difference?

My tap water is around 7.2. My tank water is also around that. I have a piece of driftwood and I think it lowers the ph just a tad like .1

I just found a RO system at my grocery store. They labeled it as GLACIER WATER.

If I mix the RO water with my tap water, will it lower it? I think RO has a ph of 7?

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post #2 of 14 (permalink) Old 05-05-2008, 04:40 PM
 
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I would leave your tap water alone in regards to PH. All fish can adapt to the PH as long as it isnt fluctuating and, A PH of 7.2 is not bad at all.
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post #3 of 14 (permalink) Old 05-05-2008, 04:44 PM Thread Starter
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oops I forgot to mention its for Crystal Red Shrimp.
They like to be in 6.5ph

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post #4 of 14 (permalink) Old 05-06-2008, 06:33 PM
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I just purchased an RO/DI unit and did a 50% water change this past Sunday and my PH before was around 7.2. After about a couple hours it was 7.2. The next day it was 6.8. Now....one of two things could have happened. I have DIY CO2. By lowering my KH from 18 to 10, this allowed the buffering capacity of the KH to lower the PH from the addition of CO2 or the RO water has a lower PH. I am leaning on the first. My thread found here https://www.plantedtank.net/forums/wa...lants-not.html has alot of good info and discussion on KH & PH. I think (and I am no scientist) that when the RO water (that has zero KH) is added and the KH is decreased, and there is the addition of CO2, the PH will drop because there is less buffering capacity in the KH. This is only my opinion from what I have read and my own experience and testing with my new RO/DI unit.

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post #5 of 14 (permalink) Old 05-07-2008, 12:34 AM
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Quote:
Originally Posted by Luichenwai View Post
oops I forgot to mention its for Crystal Red Shrimp.
They like to be in 6.5ph
Ph can reflect a lot of unrelated things, the world is hung up forever on pH. You should be concerned with your KH, and GH most of all. With a pH of 7.2 I'm guessing you have soft water already with a KH of about 3 and a GH under 10. Some added driftwood and decaying plant matter should create a nice environment.
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post #6 of 14 (permalink) Old 05-09-2008, 07:48 PM
 
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CO2 always has the same effect on pH, no matter what your KH or anything else is. x amount of ppm will lower the pH x amount. Buffer does not enter the picture. However, removing part of your buffer by adding RO will enable any acidic compounds that are in your tank (of which there are always some, nitric acid is a byproduct of fish waste not to mention driftwood etc.) to actually take effect on the pH, which is probably why your pH dropped.
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post #7 of 14 (permalink) Old 05-20-2008, 08:09 PM Thread Starter
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I just tested my KH and GH with ADI test kits (not the test strips)

My KH is 3, PH is 7.4, GH is 6-7 (I'm not sure when to stop adding drops, when the first sign of color change? or when the color changes to a SOLID color?)

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post #8 of 14 (permalink) Old 05-21-2008, 01:05 AM
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If the color change solidifies on the second drop then the degree of hardness is between the two, so say 6.5 dGH, or somewhere between 107 - 125ppm. If you're using the Hagen kit, or any kit that specifies a 20 time multiplication of drops (most kits go by drops x 17.89), then you have a GH of 130ppm (~7 dGH). Either way your water is considered soft on a scale from very soft to very hard. A GH of at least 3 to 6 is recommended for plant health, so keep that in mind when you mix RO. As it sits, you have a nice amount of calcium and magnesium available.

You won't be able to change pH much by removing what little buffering capacity you have (bicarb / KH), getting to 7 is about all you can do without adding acids from peat etc, which will only add to the total dissolved solids, getting you further from what you really want to do. And it's really not important when you're worried about hardness for livestock where the GH should be your real concern. Even then, it's a rapid shift you want to avoid, most fish etc can be acclimated to whatever hardness and thrive, some even breed. Fish or shrimp will know little difference between 3 or 0 KH. The pH I never mention here because it is a moot point, the reason your tank is not dipping down to 4-6pH like in some wild areas is because it's not filled with rotting waste like those places. Ph that low is on the way to being battery acid, acids and carbonic waste is an entirely different aspect of pH from hardness, which is why one needs to know the difference and concentrate on the important aspect.
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post #9 of 14 (permalink) Old 05-21-2008, 01:36 AM Thread Starter
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So basically the water I have right now should be perfectly fine to Breed CRS heh?

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post #10 of 14 (permalink) Old 05-21-2008, 12:36 PM
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Quote:
Originally Posted by Carissa View Post
CO2 always has the same effect on pH, no matter what your KH or anything else is. x amount of ppm will lower the pH x amount. Buffer does not enter the picture. However, removing part of your buffer by adding RO will enable any acidic compounds that are in your tank (of which there are always some, nitric acid is a byproduct of fish waste not to mention driftwood etc.) to actually take effect on the pH, which is probably why your pH dropped.
You just contradicted yourself. kH is the buffering capacity...period. By injecting CO2, the pH will be directly affected based upon the ability of the kH to buffer the pH.


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post #11 of 14 (permalink) Old 05-23-2008, 10:40 PM
 
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Mmmm...don't think so. Carbonic acid, a weak acid which is formed when co2 is injected, does not interact with KH, which is carbonates. Therefore the level of KH has no bearing on the pH drop when injecting co2 as they simply don't interact. Adding x ppm of co2 will always drop your pH x amount, assuming nothing else changes.

However, KH will have an effect on the pH fluctuation when adding strong acids, i.e. hydrochloric acid or other acidic compounds. It reacts with the strong acid to lessen it's effect on the pH. Hence the buffering capability of KH.

CO2 + H2O → H2CO3 (carbonic acid) → H+ + HCO3−

Therefore the additional H+ ions drive the pH down based directly on how much co2 is injected. KH does not enter this picture.

However....

HCl (hydrochloric acid) + HCO3 (KH) = Cl- + H2CO3

So you see that the HCO3 absorbs the H from the hydrochloric acid...thereby lessening the number of H+ ions that are out there in the water and therefore, by definition, keeping the pH from dropping due to the addition of the hydrochloric acid.
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post #12 of 14 (permalink) Old 05-23-2008, 11:31 PM
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what if you have crushed coral?
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post #13 of 14 (permalink) Old 05-24-2008, 02:23 AM
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[quote=jaidexl;604743]If the color change solidifies on the second drop then the degree of hardness is between the two, so say 6.5 dGH, or somewhere between 107 - 125ppm. If you're using the Hagen kit, or any kit that specifies a 20 time multiplication of drops (most kits go by drops x 17.89), then you have a GH of 130ppm (~7 dGH). Either way your water is considered soft on a scale from very soft to very hard. A GH of at least 3 to 6 is recommended for plant health, so keep that in mind when you mix RO. As it sits, you have a nice amount of calcium and magnesium available.
/quote]

This is not true, at the first sign of color change all of the hydroniums will have been reacted

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post #14 of 14 (permalink) Old 05-24-2008, 05:25 AM
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Well, I fell like I've confirmed it with baking soda and a little neurotic experimentation (for alkalinity reagent anyway, while creating DC standard IIRC), but I guess I could be wrong. But I really don't feel like debating it, it's a negligible difference for what we're doing and the OP's water is considered soft either way they read their GH. All I can say is I've been able to change the degree of color change with a little added RO or bicarb. Try it, lemme know how it goes for you.
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