# ph problem



## spidrman68 (Jan 30, 2017)

my ph in my tanks is about 7.8. on one tank i have co2 keeping it at 6.6. if i turn co2 off at night the ph goes up to about 7.8 so i leave the co2 on 24 hrs a day on a ph controller. I have well water and straight out of the tap its 6.0. if i let it set overnight it goes up to 6.8. i understand why and thats not the problem. what i dont understand why it goes from the 6.8 up to 7.8 over time in my tanks. please help.


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## mbkemp (Jul 4, 2015)

What kind of substrate are you using?


Sent from my iPhone using Tapatalk


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## spidrman68 (Jan 30, 2017)

1 is sand, 1 is soil and sand,1 is small brown aquarium gravel


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## spidrman68 (Jan 30, 2017)

oh and i have one with no substrate in it, just a gold fish


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## hoppycalif (Apr 7, 2005)

Welcome to APC! CO2 in water forms carbonic acid, which drops the pH according to how much dissolved CO2 you have. So, when you have the CO2 turned on you have a 6.8 pH, and when it has been off over night the pH goes up to 7.8. That is the effect of having about 30 ppm of CO2 in the water during the day.

Well water often contains a lot of dissolved CO2, so well water tends to have a higher pH after the water has been out of the well for some time, as the dissolved CO2 leaves the water. I'm not sure if that is what you are asking, but if not, ask again in a bit more detail, and one of us here is likely to give you a better answer. The swings in pH due to adding CO2 to the water doesn't bother the fish or the plants.


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## spidrman68 (Jan 30, 2017)

In the tank with CO2 it’s fine because I leave the CO2 on 24 seven on a ph controller. It’s the other tanks without CO2 I’m concerned about they have a constant 7.8 PH and I feel that the fish and plants should be lower around the 7PH. How do I get the pH in those tanks to come down lower without chemicals?


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## hoppycalif (Apr 7, 2005)

Most plants will do fine at a 7.8 pH. That pH is probably a result of having a high KH - carbonates in the water. There are plants which do better at lower pH - softer water, but a lot do fine with the harder water. The same is true of fish. If you are using CO2 to lower the pH you still have hard water, so the plants/fish, which prefer softer water, will still not do as well as they would with softer water. If you are determined to have fish or plants that prefer softer water you need to dilute your tap water with RO/DI water so you have softer water. Nothing else you add to the water can substitute for that.


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## spidrman68 (Jan 30, 2017)

i have an ro unit from my salt water i will try mixing some with tap water. thanks.


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## spidrman68 (Jan 30, 2017)

btw my tap water is 9 gh and 3 kh


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## hoppycalif (Apr 7, 2005)

spidrman68 said:


> btw my tap water is 9 gh and 3 kh


I think I would try 1/3 RO water and 2/3 tap water. That might get your KH down to 2 dKH.


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## spidrman68 (Jan 30, 2017)

If I understand kh correctly isn’t that what buffers the water so my ph doesn’t fluctuate? Is there an acceptable low kh that would still allow my water to buffer my ph?


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## hoppycalif (Apr 7, 2005)

No, by definition KH is not a buffer. A buffer is composed of a weak acid and its conjugate base. In the case of KH, the buffer is carbonic acid, H2CO3, and its conjugate base, bicarbonate, HCO3. No matter how high the KH of the water is, the pH will change the same amount if you add a fixed amount of CO2 (some of which becomes carbonic acid in the water). KH determines what the pH is when there is CO2 in the water, and there always is at least a small amount, from the CO2 in the air. That means you can adjust the pH by adjusting the KH.

The buffer, that is KH and Carbonic acid, will buffer the pH against other weak acids (other than carbonic acid) over a limited range. But, it doesn't do anything at all to keep CO2 from changing the pH.


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## spidrman68 (Jan 30, 2017)

So last night I left my co2 off and this morning my water was 8.1. If I don’t use ro water what is my best plan?


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## spidrman68 (Jan 30, 2017)

Btw you were spot on!!! With the 1/3 ro 2/3 tap,2dkh.


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## spidrman68 (Jan 30, 2017)

I’m confused, no kidding, because I’m reading all over that my kh should be at LEAST4dkh or I’m in serious danger getting ph drops because of nitrates and other acid build up in my tanks. I’m not the greatest with doing water changes and vacuuming, Yet when I test my tank water, this is a 10g tank with nothing in it but a dirty large goldfish, my ph reads 8 and nitrate is 30ppm and in my planted tank I add nitrates and they are at about 20-30ppm yet when the co2 is off overnight my ph is 8.1. What am I missing here?!? Frustrated!


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## hoppycalif (Apr 7, 2005)

The conventional wisdom about KH is incorrect. Since there is always some dissolved CO2 in a container of water that is exposed to the air, increasing the KH just increases the pH of the water. The buffer that is carbonic acid and carbonate is not a very effective one. I suspect it does keep the pH from changing when tiny amounts of weak acids, from decaying plant matter, for example, are added to the water, but I doubt it will stop a change in pH when acetic acid is added. Nitrates are not acidic so they don't affect pH. I have never seen or heard of anyone getting a big drop in pH in an aquarium, other than by adding more CO2 to the water. But, that is just a way of changing the pH at which the buffer stabilizes the pH. All buffers can be adjusted to stabilize at a specific pH by adding or subtracting the acid component of the buffer.

Buffering is a confusing subject! People who try to adjust their tank water pH down by adding hydrochloric acid find that the drop in pH they get only lasts for a short time. Then the pH goes back to what it was before adding the acid. That may be a result of the carbonate/carbonic acid buffer. My shortage of education is such that I don't know if that is how a buffer typically works.

You seem to have both a low KH, now that you diluted the water with RO/DI water, and a high pH, which would normally be low due to the low KH. So, you must have something else in the water that is keeping the pH high. What are all of the chemicals you add to the water? (GH booster, fertilizers, pH Down, etc.)


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## spidrman68 (Jan 30, 2017)

I have several tanks that get nitrate,phosphate, potassium and csm+b. One gets co2 injection. But I also have one that only has a goldfish in. No substrate NOTHING but water and goldfish and that tank also has the same parameters as the others. 3 dkh and 7.8 ish ph.


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## spidrman68 (Jan 30, 2017)

Btw the goldfish tank gets nothing added except Pond fish food, which is not what the other tanks get. I’d say this tank is completely isolated from the other ones as far as how it’s maintained .


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## hoppycalif (Apr 7, 2005)

Have you ever had an analysis done on your well water? A high GH with a low KH has to mean your water has lots of calcium and/or magnesium but not in the form of carbonate compounds. Maybe you have sulfates instead?? But, a high pH suggests high KH. How old is your KH test kit?


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## spidrman68 (Jan 30, 2017)

The one in question with the 8.1 ph and 3 dkh gets ferts via the ei method and injected co2 nothing else but flake fish food. I’m thinking there is something in my tap water seeing that the issue is throughout all of my tanks. If I have my water tested what is it I should be particularly aware of? Btw my tap water is 9 gh.


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## spidrman68 (Jan 30, 2017)

My test kit isn’t that new. But back when I got it I tested my tap water and logged the nitrates phosphates ph(right out of tap and 24 hr gas out) kh and gh and the record shows the same now for all. Ph is 6.5 then gassed out to about 8.


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## hoppycalif (Apr 7, 2005)

spidrman68 said:


> The one in question with the 8.1 ph and 3 dkh gets ferts via the ei method and injected co2 nothing else but flake fish food. I'm thinking there is something in my tap water seeing that the issue is throughout all of my tanks. If I have my water tested what is it I should be particularly aware of? Btw my tap water is 9 gh.


I would look for anything that looks unusual, like a calcium and magnesium ppm much higher than the GH that you get by using your test kit. And, anything about the alkalinity of the water, which would look odd compared to your measured KH. Water companies do a group of tests to find out what is in their water. It might be too expensive to get all of those tests done on your well water, but I don't know another way to find out what is odd about your water.

In your shoes I would be looking at prices on RO/DI systems, and thinking about how I would use it if I had it. I would also consider a water softener, if I also was having other problems with hard water. Water softening would make a RO/DI system last longer, too. But, softened water is not good for an aquarium, even though some people use it.


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