[zsxking]

I use RO water and add back mineral for my planted shrimp tank. The kH is 0~1, but pH is 7.8. I need it to be like 6.5. From what I read, pH is lowered by reducing kH/use RO water, but that won't work in my case.

How will I be able to lower pH while kH is already 0?

 

[WaterLife]

R/O water should have a pH around 5.5 or so. So adding 5.5 pH R/O should "dilute" your 7.8 pH water, thus lowering it.

Otherwise you can use other acidic sources via active substrates (acidic buffering substrates such as ADA Aqua soil), tannin/humic acid sources like peat moss, Indian Almond Leaves, Alder Cones, Cholla wood, driftwood tannins, etc. I think there are tannic/humic acid tinctures (liquid), and I think I've heard of them in concentrated powder forms as well, though research would need to be done to know how to go about properly/safely using them.


EDIT: Oh I missed the part about it being a shrimp tank. I would assume this is for soft acidic Caridinas, in that case I would definitely recommend a active acidic buffering substrate. It keeps the water stable in the acidic range, which both (acidic water and stability) are crucial to keep Caridinas healthy. I am not all too familiar with what substrates are best for that, but ADA aqua soils are common. Browse them. You can ask for recommendations on The Shrimp Spot forum (tons of experienced help there) and/or do searches for best Caridina shrimp substrates.


With a KH of 0-1 though, and using R/O water, your pH should be a lot lower.
What's your GH?

If you have to, (actually it is really recommended when dealing with shrimp, especially Caridinas), use 100% R/O water and just remineralize.
If you are already, what remineralizer product(s) are you using?

 

[zsxking]

The tank is established over a year, decently planted with driftwood, Fluval Plant and Shrimp Stratum as substrate. It's recently converted to shrimp only tank. I'm already using RO water, remineralize with Seachem Equilibrium, target TDS 150, GH 5.

R/O water should have a pH around 5.5 or so

So this got me confused the most. My RODI water has pH = 7.6, TDS 0. Does that mean my water has less CO2 dissolved than normal? AFAIK, the only other factor for pH between kH is CO2. But I don't want to run CO2 if possible...

 

[dzega]

check your PH test kit.
PH=7.6 happens at like KH=7 TDS=200 or something like that

 

[Diana]

What happens if you set out some RO water, exposed to the air for 24-48 hours, perhaps run a bubbler or small pump (reaction happens faster- half hour to an hour)?
If it is low in CO2, then it would pick up CO2, and this would lower the pH.

The organic materials listed by WaterLife ought to work, do you know if they are OK with shrimp?

Are you using API kits? The mid range pH test? (not the high range?)

 

[AdamTill]

pH is affected by KH and TDS, but they don't directly correlate. My tank runs TDS 100, KH<1, and pH ~7.2 right now (in the evenings). Lots of plants taking up CO2, without being balanced by a large animal respiratory load. Also have a cubic foot of peat in there, FYI.

To consistently drive pH low, you need a consistent acid source. Doesn't matter if your KH is 0 if there's no acid source.

 

[KevinC]

How are you measuring pH? A pH meter is inaccurate in low TDS solutions. Dye solutions (drops) are your best bet.

 

[nel]

RODI water can't have pH lower or higher than 7.0. It's completely neutral. Of course when it's fresh it can have some CO2 dissolved, but after airing it, it will go to 7.0, but cause KH=0 bringing pH down is super easy. Just let it sit with some peat and done

 

[Hoppy]

I doubt that even RO/DI water has zero KH. That would mean there is absolutely no carbonate/bicarbonate ions in the water, and the RO/DI system works absolutely perfect. We just don't find perfect stuff in real life. So, you very likely have just near zero KH. So, the CO2 dissolving into the water from the air should drop the pH below 7.0. The lowest that CO2 can drop the pH is around 5.5, so that would be why RO/DI water can have a 5.5 pH normally. If you are using a pH test kit to measure the pH, I suggest getting a new one, just in case the reagent in the current one is deteriorated.

 

[zsxking]

How are you measuring pH? A pH meter is inaccurate in low TDS solutions. Dye solutions (drops) are your best bet.

Really? Do you have more information about meter vs test solution vs test strip?

I do use pH meter, and actually did a calibration last night to make sure. Never thought low kH would affect its readings.

I don't have any other pH tester around at the moment. :frown2:

 

[lksdrinker]

So this got me confused the most. My RODI water has pH = 7.6, TDS 0. Does that mean my water has less CO2 dissolved than normal?

How old is the rodi system? might be time for some new filters in there since as others have pointed out you shouldn't be seeing those numbers out of a rodi unit.

 

[WaterLife]

What's the pH, GH, KH, TDS of your R/O water before remineralizing with Equilibrium?

 

[zsxking]

What's the pH, GH, KH, TDS of your R/O water before remineralizing with Equilibrium?

7.8, 0, 0, 0

This is the reading from water freshly out from RO/DI unit. Let it sit for an hour, lowest pH it gets is 7.6. All reading from pH meter pen.

RO/DI medium are replaced like 3 months ago.

 

[zsxking]

Just went to LFS to test the water's pH with API test kit, got 7.6, same as the reading from pH meter. So the meter should be accurate.

Also got some indian almond leaves, see if it helps.

 

[KevinC]

Here's a technical note about pH meters in low TDS: Measuring the pH of Pure Water from Cole-Parmer

Since the LFS agrees, then that removes that possibility. I'd look for a contaminant - even the tiniest amount of contamination could raise the pH since there is nothing to counteract it (no kH). A tiny bit of calcium carbonate residue anywhere in the storage tank or the presence of old snail shells in the tank could do it.

 

[Diana]

It sure would not take much of anything to make the pH drop a bit. Lets hope the IAL work.

 

[jw.cS]

I use RO water and add back mineral for my planted shrimp tank. The kH is 0~1, but pH is 7.8. I need it to be like 6.5. From what I read, pH is lowered by reducing kH/use RO water, but that won't work in my case.

How will I be able to lower pH while kH is already 0?

If I may be so bold as to not answer your question and offer some unsolicited advice. I am assuming that you are doing this for your shrimps? If so, then don't worry about the pH. They like consistency instead of any magical number. You have already given them a head start by using RO water and the active substrate. This combination alone will buffer and maintain a pH of <7. Have you tested the actual pH of the tank water?

If you are using the RO as top-off water then you shouldn't be fiddling with the water chemistry. Just add RO as is to the tank. Your Fluval substrate will do all the work. In fact, if you are using it for water changes then it shouldn't matter very much either since you shouldn't be removing >25% anyway. Adding back 25% straight RO and reconstituting with Seachem Equilibrium (raises GH, not KH) is more than sufficient. Again, that substrate will be doing all the work of stablizing your pH. I mean, how off can RO water be? The dilution factor alone from small water changes will be corrected by that substrate of yours.

Why even bother with the IAL? It doesn't have any magical properties that your substrate or leaves from your backyard wouldn't have. In ugly, barren shrimp tanks, devoid of surfaces for microflora/fauna to grow on, IAL or any other decomposing media would be beneficial. But you have a planted tank with driftwood, why spend money on IAL? The ability of a few leaves to change the pH of a 40 gallon tank is negligible when compared against the power of the substrate.

Pre-treating RO water for pH before adding to a tank with an active substrate: you are needlessly micromanaging IMHO. :grin2:

---

Up until 2 months ago, I've kept dwarf shrimps in a densely planted Eco-Complete tank with RO water. Nobody complained and they interbred. Since then, I've added some active substrate for no other reason than "why the heck not...everybody is doing it....let's see what's all the hoopla over." *laughs*

---

EDIT: So you're still adamant about altering the pH of that RO water. I recall an oversea member here recently recommended putting some pure peat (with no additives) in a bag and throwing it into your RO water storage unit. When the pH is to your liking then remove it. When the peat bag sinks, its usable life is exhausted so use some new peat. Alternatively, use some of your current Fluval substrate or any other similar active substrate in a bag. It should also alter the pH of your RO water. Although this will raise your TDS: chasing one parameter only to ruin another. ^__^

 

[zsxking]

Yeah, I understand that consistency is the most important point. But since it is so off from what considered to be good range for the shrimp, I can help but feeling concern to an extent. For example , could it be some other problem that I am not aware of that cause the high pH? Also I'm curious. There seem to be something is missing in my understanding of how pH and kH works. Even though I didn't end up fixing the pH, it will still be interesting learning. But so far, I find no sound explanation of why and how could RO/0 kH water has pH as high as 7.6.

 

[dzega]

ditch the pen ph meter and use drop/color test insted.
i found my pen was inacurate just few days after calibration

 

[WaterLife]

I have no idea why your pH is high as it is directly out of the R/O DI unit with the readings you mentioned. I can't think of a possible reason for it.

Maybe your rinse the test tubes with tap water that has a 7.6-7.8 pH and it contaminates the R/O water in the test tubes? Or maybe there is calcium deposits built up in the test tubes (after rinsing and putting away, the water evaporated, but left behind calcium). Still doesn't make much sense though if you are testing 0 for everything.

Maybe the tests are faulty. It just doesn't make sense to have 0's across the board and have a higher alkaline pH.

But anyways, with a 0-1 KH, it should be easy to alter the pH and so adding a acidic source as mentioned previously (Indian Almond Leaves) should lower the pH easily. Warmer temps release tannins faster. Test it out and see how low your pH goes down too. I personally don't dabble with soft acidic water set ups so I don't know how much IAL is necessary for you to reach desired pH in your set up (so don't ask me ).

What substrate are you using? An active, acidic buffering substrate alone may be enough to get your desired pH.