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Discussion Starter · #1 ·
I just added a pressurized CO2 system to my 29g tank. The issue I'm running into is that my tap water's KH is about 1 (or less than 1). So, if I were to aim for 30ppm CO2, that means my PH would be 6.0, based on the pH/kH/Co2 chart. I would like my pH to be more like 6.8, which means I need a KH of about 6.0 to have near 30ppm CO2.

How can I buffer my water to achieve the KH/PH/CO2 that I desire? I have pH buffers for my cichlid tank that increases KH and sets pH to 8.2. Should I add that to my planted tank's water then use CO2 to bring the pH back down to 6.8, and try to balance all of that, or is that asking for trouble? I do have a pH controller on it's way to help with CO2 dosing as well.

Thanks for any input!
 

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Plant Clown
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pH swings due to CO2 in the water column are meaningless. You're worrying way too much. If your pH is fine during dark hours, then you can put away your test kit for good.
 

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Discussion Starter · #3 ·
pH swings due to CO2 in the water column are meaningless. You're worrying way too much. If your pH is fine during dark hours, then you can put away your test kit for good.
I'm not sure I follow. Are you saying that the pH change due to CO2 isn't real, the reading just changes? Or does the PH actually change? Does this pH shift have any effect on the fish?

Also, once I get my ph controller, the pH will be constant day and night. If I were to set the pH to always be at 6.0, would this have a negative effect on the fish that have higher pH requirements of, say 6.5 or up?
 

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Plant Clown
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Your fish will be more sensitive to the amount of CO2 in the water than to the pH swing it causes. This can be illustrated by the fact that, given a higher KH, fish will still start "gasping" at the surface once CO2 concentration reaches a certain point, even though, in a higher KH tank, the pH would be higher at this point than in a lower KH tank.

pH swings caused by the introduction of CO2 are temporary, and the pH will revert to normal after a few hours of allowing the CO2 to gas off.

Let's say your fish begin to freak out at 50ppm of CO2. You could increase the KH to 10, and fish would still freak out at 50ppm, even though the pH will barely have fallen. It's more important to have pH at a certain level *before* the addition of CO2, assuming you care about pH in the first place (I haven't measured pH in maybe 6 months for any of my tanks, 3 of which I keep at high CO2 levels during lighting periods).

I should also note that the KH/pH/CO2 chart is only a rough estimate at the best of times, and becomes completely meaningless once you start artificially changing any of the factors. Increasing KH, for example, will have zero effect on the amount of CO2 that is, or can be, dissolved into the water column.


There are a lot of issues to wrap your head around (I'm already trying to be selective about which ones I comment on), but, basically, if your fish are fine with the current pH, they won't have any issues with pH swings due to CO2. Your only real problem is keeping yourself from adding enough CO2 to gas out your fish. Which is where a drop checker comes in handy. With a solution of pH indicator mixed with 4 degrees KH water, the solution in a drop checker will turn lime green when your CO2 concentration in the tank reaches somewhere around 30ppm, which is generally accepted as a good CO2 level for plant growth.
 

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Fish don't generally have pH requirements. Some do have requirements for low or high KH, but not pH. If you decide to use a pH controller, you may be adding CO2 at night when it only does harm. I'm not a fan of those controllers, even though I know some people have success with them. It is much better to shut off the CO2 when the lights are off.
 

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pH? who cares?

ha! actually I thought EXACTLY the same thing starting out and have a thread I started where a member kindly held my hand explaining the whole thing to me.
(I'm very thick headed LOL)

Shifts (swings or changes) in GH, KH, TDS, osmotic pressure that's the yada yada that causes our critters issues not pH changes per say. Tested pH is a product of carbonate buffers and CO2 content in the water for this conversation. Acidic or alkaline yes but testing pH as it relates to tank water with CO2 injected what are we looking at and why? CO2 content.

Mg and calcium levels don't even factor at all in a pH reading but sure as hell change the TDS and osmotic pressure. I can easily get a tested result of 7.4pH in both 4dGH and 14dGH water. Flip a fish outta the net from one to the other either way and you just hit the critter in the face with a 2x4.

The changes in pH caused by elevated CO2 levels do not change the mineral content of the water in any meaningful way, GH and KH values are the same.
That at least I was able to prove to myself over time using test kits.

I reconstitute RO for all my tanks to the range of 4-6dGH and 2dKH using GH booster and baking soda. NPT or high tech I do them all the same.

As long as the temperature is matched I routinely swap fish between injected tanks with 5.9/6.2pH and 7.4/7.6pH low techs.
Temps the same, the TDS is very close and fish don't care. CO2 induced pH differences don't bother them in any experience I've had here.

I use Pinpoint controllers and hold a steady, low pH without effect on fish or tank bacteria. Plants grow and pearl. Controllers are just another pricey toy,,, but I like them.

Drop checker with 4dKH solution for visual monitoring.
Having a known KH buffer value in my water I refer to the chart and set the controller, that's it, done. Running three tanks this way holding with a 0.40 set point. 5.8/6.2pH is the average here and no issues. 2dKH again is what I mix my RO value for so I set accordingly then adjust until the drop checker is yellow green or the fish are distressed then back off slightly. Once you've done it a few times it's old hat.
 

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Like the others have said, and I've been saying for a decade.... pH changed related to CO2 aren't relevant. pH in itself isn't that important. As long as your kh and gh stay constant(and co2 doesn't change them... so it will) you are fine and your fish will be fine.

When you start screwing around with kh/GH you really risk causing a lot more problems. Think of co2 as causing a "false" reading for pH. It isn't really "false" but it isn't the same as having a much lower kh/gh/ph.

Just leave it be.
 

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Discussion Starter · #10 ·
Thanks guys, I think I have a much better understanding of all this now. So essentially, the pH doesn't matter, per se, if CO2 is injected as long as other parameters are all in tact. The way I think of it is exactly as OverStocked said, is a "false" reading (not technically, but at least for our purposes), and as long as our other parameters (mainly kH) are ok, the fish will be happy.

So essentially, I can set my pH controller to 6.0, and as long as other water parameters remain steady, I will always maintain the optimum CO2 level, no more, no less, and fish that "need to be" at 7.0 ph or higher (the natural value of my water), will be fine, and it would also not overdose CO2 and "gas out" the fish.

pH Controller = 6.0 = Happy fish and Pearling Plants?
 

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Yes ,lot's of fish killed with this advice.:confused1:
Maybe additional advice to do so slowly, while observing the fishes reaction's?If fishes are also present.
surface agitation is a plus. A good relationship in the tank of oxygen and co2 will help.

I usually up the co2 every 3 or 5 days. If im going for a certain target.
 

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pH Controller = 6.0 = Happy fish and Pearling Plants?
I think its a little more complicated but at the same time more simplier than that. I never check my PH. I dont care personally. Only when things go wrong and I get deaths thats when I start checking.

I run PH maybe around 6.5 natually.
 

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back to Crisp330's issue about low KH

The issue I'm running into is that my tap water's KH is about 1 (or less than 1).
Getting back to Crisp330's issue regarding low KH... The thread has mostly been convincing Crisp330 that CO2 doesn't matter so much as long as GH and KH are steady. Finally, Crisp330 decides to just set the pH controller to 6.0. What is the relevance of the very low KH? Will that be a problem for the fish that are thought to need a "higher pH," but which, if pH is actually not what's relevant, may need a higher KH?
 

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as long as kh is 1 or higher, the water is sufficiently buffered. weekly water changes and good tank maintenance will assure that no problems are had with buffering

and before said posted just drops his ph to 6.0 with c02. he first might want to do it slowly over time to see how his fish react. if plants aren't producing enough oxygen and using enough carbon to do so.. then fishies might die.. so take it slow. and enjoy
 
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