KH, CO2, help me please.
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bs6749
Aquarium Advice Addict
First let me ask what your water parameters are as far as dKH and pH. For the most part you won't need to adjust your pH unless you are trying to breed or are attempting to keep delicate species. A KH of 4-5 degrees will provide decent buffering in preventing pH swings, obviously higher numbers would provide a better buffering capacity. For an "average tank" I'd try to shoot for a dKH range of 8+.
Hi bs6749, thanks for responding. Let me explain my situation...I just filled my 75 gallon with a split of R.O. and tap. If I am reading my GH and KH test kits properly, then 1 drop = 1 degree of hardness. Therefore, my tap has about 7-8 degrees GH, 7 degrees KH, and a PH of 7.2-7.4 straight out of the tap, and higher when it has sat out. Not that my water is hard necessarily, but my goal is a pH of 6.8, which my tap does not have. I have been experimenting with mixing tap with my new R.O. unit, but I am uncertain where I should keep my GH/KH levels at, and it's driving me crazy. If I keep my KH at that 4-5 range, then my pH goes above 7.0. I can go into this further, but see what you think about what I've said so far. Thanks!
Also, the mixed R.O./Tap I added to my 75 was a pH of about 6.8-7.0, but once I turned my filter on and tested it the next day, the pH shot up to at least a 7.4, maybe even 7.8 (the test kit is kinda hard to read sometimes). Other have claimed this is due to the release of CO2 with the aeration, which drove the pH up. What do you think?
rich311k
Aquarium Advice Addict
My KH is 1 and I have no issues with CO2 injection.
roka64
Aquarium Advice Addict
- Joined
- Mar 21, 2006
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- 13,858
I'll move this to the FW General Discussion.
jsoong
Aquarium Advice Addict
Assuming that there is ONLY water & bicarbonate ions (ie KH) in the system, there is a linear relationship between CO2 level, pH & HCO3 level.
This is the calculator: Measuring CO2 levels in a Planted Tank
The equations do not hold if there is any other buffer present. To check that, equilibrate your water to room air (say airstone for a few hours), then measure your KH & pH. The calculator should give you a CO2 level of 3 or so <the atmospheric CO2 level>. If it is not, you have a second (or third) buffer present.
If you have only bicarbonates in the system, then aim for a KH of 2-3 degree minimum. (This gives a pH in the low 7's.) If there are other buffers present, those buffers will hold the pH steady (though at a different value). Unfortunately, hobbyist can't really measure that, the best you can do is to look at your water co.'s water analysis & see what you got.
This is the calculator: Measuring CO2 levels in a Planted Tank
The equations do not hold if there is any other buffer present. To check that, equilibrate your water to room air (say airstone for a few hours), then measure your KH & pH. The calculator should give you a CO2 level of 3 or so <the atmospheric CO2 level>. If it is not, you have a second (or third) buffer present.
If you have only bicarbonates in the system, then aim for a KH of 2-3 degree minimum. (This gives a pH in the low 7's.) If there are other buffers present, those buffers will hold the pH steady (though at a different value). Unfortunately, hobbyist can't really measure that, the best you can do is to look at your water co.'s water analysis & see what you got.
Well, when I tried to reconstitute my R.O. with the Sodium BiCarb (by Mardel) I would add the LEAST amount possible, which would be HALF of spoon they give you to use. It states:
Use one level spoonful of Buffer-Up per 10 gallons of water. This amount gives 40-60ppm increase in the buffering capacity without significantly changing the pH.
So, like I said, I would use HALF A SPOONFUL for 5 gallons. This would give me a pH in the lower 7 region, but when I would test for how much KH I had in the water, it would be very low, like 1 degree. Therefore, it is basically impossible to achieve that minimal 2-3 dKH range without putting my pH up too high. This is what I posted about in my other thread about the Seachem Buffers:
100% Carbonate buffers (which buffer at a higher pH and pretty much amounts to using full tap water again) cannot be used. Also, I like to keep my Macs in planted tanks; hence phosphate buffers (which are notorious for causing algae) are out of the question. The only product out there that are not 100% carbonate and phosphate buffers is a pair of products by Seachem called “Acid Buffer” and “Alkaline Buffer”. Used together in varying proportions, I can achieve any pH of water between 3 and 10 that I want.
It sounds as though the Sodium BiCarbonate will keep buffering my pH too high to achieve the desired KH levels I want. These Seachem products may be better, but I haven't tried them yet. Anyone else used them?
Use one level spoonful of Buffer-Up per 10 gallons of water. This amount gives 40-60ppm increase in the buffering capacity without significantly changing the pH.
So, like I said, I would use HALF A SPOONFUL for 5 gallons. This would give me a pH in the lower 7 region, but when I would test for how much KH I had in the water, it would be very low, like 1 degree. Therefore, it is basically impossible to achieve that minimal 2-3 dKH range without putting my pH up too high. This is what I posted about in my other thread about the Seachem Buffers:
100% Carbonate buffers (which buffer at a higher pH and pretty much amounts to using full tap water again) cannot be used. Also, I like to keep my Macs in planted tanks; hence phosphate buffers (which are notorious for causing algae) are out of the question. The only product out there that are not 100% carbonate and phosphate buffers is a pair of products by Seachem called “Acid Buffer” and “Alkaline Buffer”. Used together in varying proportions, I can achieve any pH of water between 3 and 10 that I want.
It sounds as though the Sodium BiCarbonate will keep buffering my pH too high to achieve the desired KH levels I want. These Seachem products may be better, but I haven't tried them yet. Anyone else used them?
