Calculating hardness from water report - The Planted Tank Forum
Old 09-05-2019, 07:04 PM Thread Starter
Algae Grower

Join Date: Sep 2018
Posts: 11
Calculating hardness from water report

Hey guys, like a lot of planted tank rookies, I'm trying to wrap my head around water hardness and what it means. I don't have a hardness testing kit yet, but I do have the hardness portion of my town's tap water analysis.

KH: After lots of digging, I found that "One degree KH is equal to 17.9 mg/I (ppm) CaCO3." In my case, I have 197 mg CaCO3/L = 11 dKH.

GH: Calculating GH seems to be Ca, Mg and other ions also divided by 17.9 mg/l, but I can't find what other ions it means. Assuming that the non Ca & Mg ions are just traces, my dGH is (41.1 + 22.9)/17.9 = 3.6 dGH.

The PH is right where you'd expect it to be with a high dKH, 8+.

I've attached the analysis so you can see for yourself, if you'd like.

So, a couple questions:
- Is my math-ing correct here?
- What does this mean for my tank's plants and inhabitants?
- If something is out of balance and needs to be adjusted, how do I adjust it (preferably without RO/DI)?

Thanks, Dan.
Attached Files
 File Type: pdf Hardness Parameter.pdf (284.7 KB, 14 views)
Dan Newman is offline

Old 09-05-2019, 09:07 PM
Planted Member

Join Date: Dec 2011
Location: Rockport, Texas
Posts: 209
Your water report has T-alkalinity (=total alkalinity, expressed as CaCO3). That's the value you should use for KH, and you have 395/17.9= 22dKH.

Similarly, they report hardness as CaCO3 and you should use that value. You have 197/17.9=11 dGH.

You have moderately hard water with fairly high TDS, which is remarkably similar to mine. You won't be able to spawn discus or anything that requires soft water, but otherwise you should be OK. I can grow just about any plant in my hard water.
Mark Fisher is offline
Old 09-05-2019, 09:34 PM
Wannabe Guru

Join Date: Feb 2017
Location: PA
Posts: 1,354
Quote:
Originally Posted by Dan Newman View Post
- If something is out of balance and needs to be adjusted, how do I adjust it (preferably without RO/DI)?

Thanks, Dan.
Don't want to download an unknown file, so I can't comment on the water parameters, but it looks like @Mark Fisher took care of that.

As far as lowering GH and KH, without RO/DI/distilled water, here is another option, but I haven't seen a price on it: Softenizer | ADA - PRODUCT - WATER CONDITION & TERATMENT.

Discussion on it begins here: https://www.plantedtank.net/forums/1...l#post11238003.
Deanna is offline

Old 09-05-2019, 09:42 PM Thread Starter
Algae Grower

Join Date: Sep 2018
Posts: 11
Awesome, thanks Mark. I don't plan on having Discus, so no worries there.

Edit: Thanks Deanna, I'll look into that too.
Dan Newman is offline
Old 09-05-2019, 11:34 PM
Wannabe Guru

Join Date: Jun 2017
Posts: 1,147
Quote:
In my case, I have 197 mg CaCO3/L = 11 dKH.
Quote:
Your water report has T-alkalinity (=total alkalinity, expressed as CaCO3)
Keep in mind the KH test doesn't tell you how much calcium you have. It just measures carbonate ions which can be from calcium carbonate, magnesium carbonate, potassium bicarbonate, or sodium Bicarbonate. Your water report shows you have Ca, Mg, sodium and potassium in your water. Since the KH test cannot identify the source of the carbonate, the value is "expressed as" or is equivalent to 197mg of calcium carbonate dissolved in water.

The same applies to GH it detects calcium, magnesium, beryllium, strontium, and barium. beryllium, strontium, and barium are typically present in tap water but at very low levels. Since the GH test cannot distinguish between these elements the value is again expressed as a calcium equivalent value.

Your actual calcium value is 41mg/L and your magnesium level is 22mg/L. You do not have 197mg of calcium in your water. You have a 2 to 1 ratio of calcium to magnesium which is great by itself for plants.

Also note that if your carbonate was strictly from calcium and magnesium carbonate your PH would be very close to 7. However your water report shows you have an elevated level of sodium, 104mg/L. Most of the sodium is apparently present as bicarbonate in your water and that can easily push the PH up to 8. Your water utility is probably adding sodium bicarbonate to your water to keep your PH high to minimize water pipe corrosion.

The main issue I see it that the high PH will make it hard to keep iron dissolved in the water. At a PH of 8 it will precipitate out and settle into your substrate and may not be readily available to your plants. You can use the previously mentioned water softening device to lower the mineral content and PH of your water. However keep in mind it will also reduce calcium and magnesium levels. If you reduce Ca and Mg levels too much you will need to add some to your water.
Surf is offline
Old 09-06-2019, 02:02 PM Thread Starter
Algae Grower

Join Date: Sep 2018
Posts: 11
So, it seems the main concern would be the PH then. Would using some kind of acid (vinegar?) or aquarium specific PH lowering solution (API Ph Down?) help, without messing with the good parts of my water (Ca and Mg)?
Dan Newman is offline
Old 09-06-2019, 03:41 PM
Planted Member

Join Date: Dec 2011
Location: Rockport, Texas
Posts: 209
I wouldn't bother. My water also hovers around 8.0, and I dose chelated iron along with NPK. The tank has been running continuously for almost 4 years and no iron deficiency has developed.

I have attached my water quality report FYI. Page 1 is the intake (lake) water and page 2 is the treated (output) water. It's very similar to yours.
Attached Files
 File Type: pdf WAT_monthly-report-2019-july.pdf (385.7 KB, 3 views)
Mark Fisher is offline

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