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Discussion Starter · #1 ·
I just started injecting CO2 and am noticing a big pH drop from about 7.5 down to 6. I need to buffer the pH on the low side, to around 6.5, and was wondering what product(s) might be good for this? My RO water is at about 6.4 pH, 1 KH, 1 GH, going into the tank.
 

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How did you test the GH and KH of your RO water? And, the pH testing of RO water—and especially RO/DI water—usually gives inaccurate results. Also, how and when did you measure the pH drop? The pH drop you’re reading is most likely a very temporary drop. Do you have fish in the aquarium? are they gasping? Up at the top? Swimming frantically up and down.a corner or the side? Or acting fairly normal?

Give me a few more details and then I and others can give you some suggestions. I will also look up the links to some discussions that can point you in the right direction. As soon as I get the water changed in a tank I blacked out for three days. Oh, and get my hardscape moved around, annoy the shrimp, clean the submersible pump assembly, and plant my crypt parva. Lots to do, but it’s more fun than housework!
 
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That ph drop is due to your CO2 injection. Buffering it will only change both before and after ph, and not affect the amount of CO2 in the water.

If your fish are tolerating a 1.5ph drop, then it's all good. If they are gasping at the surface, acting listless, or darting around frantically, then you need to dose less CO2. Most people shoot for a 1.0 to 1.2 ph drop from their CO2.
 

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Discussion Starter · #4 ·
How did you test the GH and KH of your RO water?
I used API's liquid tests for KH and GH measurement. Tested 24 hours after dispensing, also.

And, the pH testing of RO water—and especially RO/DI water—usually gives inaccurate results. Also, how and when did you measure the pH drop?
I measured the pH drop 3 times over 3 days with a Milwaukee Instruments MC120 meter, noting the before and after 2bps CO2. It consistently came up to the same pH and down to the exact same number with CO2 three times and liquid pH tests yielded similar results, prior.

The pH drop you’re reading is most likely a very temporary drop. Do you have fish in the aquarium?
No, I want to figure this out first so no fish - just a planted tank for now. Since there are no fish, I would like to experiment a little until I can get the CO2 somewhere below 30 with a pH of around 7 and KH hovering around 6. I was thinking of just adding Neutral Regulator until I can get this close to this result with and without CO2 but wasn't sure if I could get away with it being that easy, lol.
 

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I wouldn't concern yourself with getting the ph into a certain place. Fighting your water with additives is an excersize in futility. You're going to have fluctuations you can't avoid. I would remineralize your GH a little bit higher (maybe to 4-5 dGh) and turn your CO2 down a bit. You can absolutely have a ph of 6 and be fine.
 

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The API test kit for GH, which I use and like, has directions that say 1 drop = 1°GH. But, what if you have zero GH?(see note 1) It isn’t going to turn color until you put a drop in. This was actually a problem for me because I let myself get persuaded to use one of the active soils. When they’re new, fight to keep the GH above zero can be tough. I was seeing my GH go from what I thought was 2° to 1°overnight, then realized the drop could actually be more than 1°! Measuring GH that is below 1 can be done, as well as measuring between degrees of hardness. I only ever measure to 1/3° now (1/3° is approximately 1 meq), and don’t do that often although I always test to the 1/2° after water changes. I can tell you how to do that with your API test kit if you want.

That said, before you put fish in there, you’re going to want to raise the GH. Like many, I have kept tetras and corys, which are “soft-water fish,” successfully in tanks that have water that is considered moderate to hard. Currently, I have Corydoras hasbrosus and dwarf neons happily inhabiting a tank with 4-5°GH. I keep it that high because I have mystery snails and snails keel over in water that is too soft. I also keep the pH up around 7.0 for the same reason. That tank also has one lonely Amano shrimp in it. The other three died before I found what works to keep the GH up.

To raise GH, there are a lot of products that can be used, with Seachem’s Replenish and Equilibrium probably the top two chemical additives. You can also use crushed coral or aragonite, but they’re hard to figure out and will raise the KH as well. Myself, I’m kind of a Seachem fan, as are many on the forums. I have found that Seachem Equilibrium works better to raise GH and last than their daughter company‘s Aqua Vitro Mineralize. I am not a chemist, so I can’t explain why the sulfates used in the Equilibrium last longer, meaning aren’t exhausted as fast, than the chlorides used in Mineralize. I think I’ve got it figured out in my head, but like I said, not a chemist and am old enough that in high school chemistry we still used the Bohr model.(see note 2) As for KH, although there are some posters that say to go ahead and use baking soda, I really don’t recommend it. Baking soda is sodium bicarbonate, which after reacting with an acid, liike the carbonic acid from your CO2, wil have one end product of salt (NaCl), which can build up if you have a few weeks in which you’re not diligent enough with your water changes and that’s not good for many fish—like corydoras for example.

I don’t know what plants you want to kee, but many can tolerate water that is moderate to slightly hard. I see a lot of posts on here from people who say they keep their GH at 1° and their pH at 6.4-6.6, but that’s not for everyone. I love my snails—I even name them!—and want to enjoy planted aquariums, but the fish and invertebrates are still the reason I’m in the hobby.

If you want the procedure to test <1° GH or KH, let me know. It’s easy; after all I figured it out.

1 The same goes for the KH test of course.
2 Less you think me too old a fossil, I am updated on the current understanding of electron energy levels.
 
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Oops! I forgot to tell you a few things about Seachem Equilibrium:

1) Measure by weight if you have a scale that measures to the tenth/gram. Much more accurate than by parts of a teaspoonful. The smaller your aquarium is, the more important (IMHO) to measure. The reason to go by weight is that the powder can compact with time and handling of the bottle, making your measurements off a little maybe. Still, the scales are cheap online.

2) Since Equilibrium contains sulfates
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, which are not as easily dissolved in water as most GH chems I know of, you can’t dump it into the aquarium straight. It does have to be pre-mixed with some your RO water. When you stir it up, the water will become slightly yellow-brown and a small amount of sediment will remain on the bottom of the cup/glass/beaker/whatever. That’s normal. If you have a lot of sludge on the bottom, you are mixing too much Equilibrium for that amount of water and need to use more water to mix with. No matter what, it seems as if I always have a tiny bit of sediment, including a couple of brown flakes.

3) Equilibrium will raise your KH, too! This surprised me, because I hadn’t really been expecting it. So, don’t adjust KH in your aquarium until after you’ve used the Equilibrium. The pH rise is from the Potash, which in this case is potassium sulfate, which is a carbonate.
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It’s not that uncommon for things that raise GH to raise KH also.

4) Despite the oddities, I think Equilibrium is a great product. It’s dependable, quality, relatively inexpensive, and it works. No, I am not getting paid to push the product.


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potassium sulfate, calcium sulfate, magnesium sulfate, ferric sulfate, manganese sulfate
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Yes, I know there’s no carbon in it, It’s still a carbonate. Look up carbonates in Wikipedia if you’re not a chemist.
 

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Discussion Starter · #9 · (Edited)
Hey thanks for the great explanations, I really appreciate all the effort put into that answer - sure - I'd like to hear how to measure 1/2 drops and such. I'm guessing 10 drops from a real dropper would be half but not sure.
 
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