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Discussion Starter · #1 · (Edited)
Hello and thank you in advance for giving me your time. I recently purchased a r/o filter because of tap water hardness and ph issues. I needed r/o water for a different hobby as well. I tried mixing tap and r/o water to obtain water in parameters I was going for. 3d of Kh and 3d Gh with a ph around 7.3 or close to. But the hardness was either real high or the kh non existant. Close as I could get was 2kh and 7gh. I purchased equilibrium and seachem alkaline buffer. I placed an air stone in my 5 gallon water bucket and the following day I added 3/4 teaspoon of equilibrium, 1/4 teaspoon of alkaline buffer, and a 1/4 teaspoon of api ph down. Checked all my test and they were exactly as I wanted 3d gh, 3d kh, and ph 7.3. Then Let it aerate overnight and the gh and kh were the same but the ph was 7.9. I added more acid 1/4 teaspoon. Got my lvl to 7.4 which I was fine with. I let it sit for a few hours came back and it was back to 7.9. Can anyone explain to me what I'm missing.
Thx Again
 

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Why not just go 100% RO water? That way you won't have to concern yourself with fluctuations / seasonal variations in your tap water; likewise, you'll find the amounts of your GH and KH additives will be stable per each water change
 

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Its wierd, but PH of water fresh from the tap VS PH of the same water after it has sat around 24 hours, especially with aeration, will actually rise. It's called outgassing, and people here will talk about Ph of degassed water vs non-degassed when theyre tweaking PH with CO2.

I started off trying to control GH/KH with equilibrium but had the same problem with my parameters constantly changing, and got too frustrated with it. The equilibrium adds gh/kh, the acid buffer consumes kh to drop ph Temporarily, and the alk buffer adds kh as I understand it. Which just makes the whole mess too complicated. I switched to salty shrimp which seems to reconstitute to 3:1 GH/KH, so if you want a little more KH you can just add that with bicarb. Much easier, and stays stable. At least for me.
 

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Discussion Starter · #4 ·
Why not just go 100% RO water? That way you won't have to concern yourself with fluctuations / seasonal variations in your tap water; likewise, you'll find the amounts of your GH and KH additives will be stable per each water change
I've read so many negative things about going pure r/o. I've read the water lacks elements the fish nead and the water would be susceptible to ph swings.
 

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You have to reconstitute RO water to put those needed elements back into it, but it is all within your control. If you provide those things that your plants need, the fish food will take care of the rest, as far as fish health is concerned.
 
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Discussion Starter · #6 ·
Its wierd, but PH of water fresh from the tap VS PH of the same water after it has sat around 24 hours, especially with aeration, will actually rise. It's called outgassing, and people here will talk about Ph of degassed water vs non-degassed when theyre tweaking PH with CO2.

I started off trying to control GH/KH with equilibrium but had the same problem with my parameters constantly changing, and got too frustrated with it. The equilibrium adds gh/kh, the acid buffer consumes kh to drop ph Temporarily, and the alk buffer adds kh as I understand it. Which just makes the whole mess too complicated. I switched to salty shrimp which seems to reconstitute to 3:1 GH/KH, so if you want a little more KH you can just add that with bicarb. Much easier, and stays stable. At least for me.
I've done a lot of research trying to figure this out. It seems easy enough when reading about it, but it's turned into a head scratcher. Thx for the advice I'll look into it.
 

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I've read so many negative things about going pure r/o.
Interesting because I use 100% RO and would never go back to tap

I've read the water lacks elements the fish nead and the water would be susceptible to ph swings.
That's true, you must re-constitute the water but the addition of salts for KH and GH to stabilize your water is straightforward
 

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Discussion Starter · #8 ·
Interesting because I use 100% RO and would never go back to tap



That's true, you must re-constitute the water but the addition of salts for KH and GH to stabilize your water is straightforward
It does seem straight forward on paper. But test after test with the products I'm using I can't keep the ph from climbing over night. I add acid get it back where I want it and again over night it climbs back up stabilizing at 7.9. Is there a coralation between kh and ph. Meaning I need lower kh to stabilize my ph at the lvls I want?
 

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Carbonates are the buffer for pH. Raise carbonates and pH rises. Lower carbonates and pH falls. KH (dKH) measures the amount of carbonates in your water, which are, by far, the only buffers of consequence in an aquarium.
 

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I've read so many negative things about going pure r/o. I've read the water lacks elements the fish nead and the water would be susceptible to ph swings.
Like what Deanna said, you have to remineralize the water if you're using pure RODI. I used Equilibrium for GH, and then mixed Seachem Acid and Alkalinity Buffers in order to buffer the water. I had great shrimp growth and pretty okay fish growth as well.
 

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It does seem straight forward on paper. But test after test with the products I'm using I can't keep the ph from climbing over night. I add acid get it back where I want it and again over night it climbs back up stabilizing at 7.9. Is there a coralation between kh and ph. Meaning I need lower kh to stabilize my ph at the lvls I want?
pH changes thru the course of the day are to be expected if you're injecting CO2 and even if you're not, what with plant uptake and off-gassing due to water circulation. Or am i missing some other concern/issue you're having?

Here's the pH of my tank for the last 7 days (KH=1.35, GH=5)
1027797
 

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Discussion Starter · #12 ·
pH changes thru the course of the day are to be expected if you're injecting CO2 and even if you're not, what with plant uptake and off-gassing due to water circulation. Or am i missing some other concern/issue you're having?

Here's the pH of my tank for the last 7 days (KH=1.35, GH=5)
View attachment 1027797
The water never makes it to the tank. This happens in my buckets of water I'm treating before water changes. I gas them off with a stone for 24hrs before I add anything. Then add what I posted earlier equilibrium first and the acid last. I then test everything and its uassly right were I want it. I then leave the air stone in the buckets for another 24 hours. Take test again, and this is the point were the ph has climbed. I add 1/4 tsp acid and repeat the process, and the ph again climbs. I haven't used the water because I haven't got it stabilized were I want it. Should I just keep adding acid?
 

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Got it...I assume you're using the air stone to churn up the water in the bucket and help with the the dissolution of equilibrium and the alkaline buffer, yes? While helping to dissolve the buffers it's dispelling/off-gassing the CO2 present in the water resulting in a rise in pH. To understand how that is so here's a CO2 chart that can better explain the relationship between pH, KH, and CO2

CO2 chart

At KH = 3 (your targeted value) you'll find the pH rise from 7.3 to 7.9 coincides with a fall in CO2 from 4.5ppm to 1.1ppm - the airstone drives off CO2, the CO2 falls, and the pH rises

To help with dissolution you might consider a circulation pump in lieu of the airstone

As to adding acid (ph down) - if the KH of your source water was higher than your targeted KH then that would be a reason to use it; however, if you're using alkaline buffer to raise KH then adding acid is counter-intuitive. And your KH should be stable - once you reach your target leave it alone
 

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Discussion Starter · #14 ·
Got it...I assume you're using the air stone to churn up the water in the bucket and help with the the dissolution of equilibrium and the alkaline buffer, yes? While helping to dissolve the buffers it's dispelling/off-gassing the CO2 present in the water resulting in a rise in pH. To understand how that is so here's a CO2 chart that can better explain the relationship between pH, KH, and CO2

CO2 chart

At KH = 3 (your targeted value) you'll find the pH rise from 7.3 to 7.9 coincides with a fall in CO2 from 4.5ppm to 1.1ppm - the airstone drives off CO2, the CO2 falls, and the pH rises

To help with dissolution you might consider a circulation pump in lieu of the airstone

As to adding acid (ph down) - if the KH of your source water was higher than your targeted KH then that would be a reason to use it; however, if you're using alkaline buffer to raise KH then adding acid is counter-intuitive. And your KH should be stable - once you reach your target leave it alone
Ok. Thx. You are correct, I use the air stone to mix and off gas. I thought if I ran the stone 24hrs before adding the chemicals it would be gassed off already allowing me to get a stable ph reading. I guess I was wrong in this thinking? So you say the initial first bucket and test that was correct is were I should stay with and not gas it off anymore or add anymore acid afterwards? If I understand you correctly the ph will swing up and down between 7.3 and 7.9 depending on the amount of co2 present in the water at a kh of 3?

Ok. Thx. You are correct, I use the air stone to mix and off gas. I thought if I ran the stone 24hrs before adding the chemicals it would be gassed off already allowing me to get a stable ph reading. I guess I was wrong in this thinking? So you say the initial first bucket and test that was correct is were I should stay with and not gas it off anymore or add anymore acid afterwards? If I understand you correctly the ph will swing up and down between 7.3 and 7.9 depending on the amount of co2 present in the water at a kh of 3?
I Think I got it now. Looking through seachem website and their products, I Believe I got the incorrect kh buffer. They have so many. I'm going with the baking soda suggestion instead. Your advice is helpful and steering me in the right direction. Thx again.
 

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I use acid base to drop KH from 25deg, I've stopped trying to manipulate PH which ends up around 8ish, but I have CO2 injection. 50% RO mix. Too many bad experiences trying to drop PH- so the livestock is selected to what what I have.
 

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Out of curiousity, what other hobby requires RO water enough to have made you purchase a system?

Also you might enjoy this 2015 thread on your same issue - I like the practical advice in the second post.

 

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Out of curiousity, what other hobby requires RO water enough to have made you purchase a system?

Also you might enjoy this 2015 thread on your same issue - I like the practical advice in the second post.

Keeping plants hydroponically or semihydroponically.

Keeping saltwater fish tanks.

Keeping a large number of plants that require low TDS water (carnivorous plants, orchids, etc.).

Just a few I can think of off the top of my head.
 

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You are a busy guy!
Haha, nahh, I don’t do all of those things. I did a cost benefit analysis of growing plants hydroponically or semi hydro, and concluded it was cheaper to just buy soil. Might have to redo that analysis over long and short term. But for now my plants are in soil and fed with fish tank water haha.

Saltwater does take up a large amount of rodi water though.
 

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Like what Deanna said, you have to remineralize the water if you're using pure RODI. I used Equilibrium for GH, and then mixed Seachem Acid and Alkalinity Buffers in order to buffer the water. I had great shrimp growth and pretty okay fish growth as well.
I bought the Seachem Acid and Alkalinity Buffers and could never figured it out how to use them together, even sent an email to seachem end they responded with a too complicated answer for me to understand. Can you please advise how you do it?

I use 30 gallons RO water and 5 tap water for my weekly water change. I do get after the 50% water change 3-4 KH and GH using just a little bit of Equilibrium for GH.

Thanks!!
 
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