Low KH, high GH, neutral PH - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 09-28-2020, 07:35 AM Thread Starter
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Low KH, high GH, neutral PH

Hi all, I have just converted my 125g from artificial to real plants, and begun CO2 fertilization for the first time. I just tested my water, and am unsure what to do (if anything) with these parameters:

Nitrate 20
Nitrite 0
dGH 16
Chlorine 0
dKH 2.25
Ph 7.2 and stable
Ammonia 0

My tap water does NOT have this issue naturally, testing my tap water gives the following:

Nitrate 20
Nitrite 0
dGH 4.2
Chlorine 0
dKH 4.48
Ph 7.2

So why is my tank GH so high, and KH so low? I have no calciferous rocks or decorations, use regular old aquarium gravel with CaribSea Eco-Complete Planted Aquarium Substrate mixed in. I just added the CO2 yesterday, it’s the ZRDR CO2 Generator system that uses the baking soda and citric acid. My CO2 indicator still shows “low CO2, and no fish are looking distressed or gasping, everybody looking happy and healthy, and I just moved conservatively from 1 to 2 bubbles per second on my bubble counter.

Is the GH/KH something I need to worry about, and what do I do about it? Everything I read regarding high GH talks about using RO water, but since my tap water isn’t the issue it doesn’t seem to make much sense to go that route.

The tank is well established, it’s been running for 6 years, the only change is adding the live plants and CO2 over this past week. I do weekly water changes, treat all water with Prime, change out filter materials regularly, and use liquid Easy Green fertilizer, occasional Easy Iron liquid fertilizer, and Excel Flourish. Non-plant decorations are mostly resin, with a few natural driftwood pieces with Java ferns attached. Filtration is a PenPlax Cascade 1500 external canister, a Marineland BioWheel 150 and a Marineland BioWheel 350.

Do I need to do anything with the GH/KH?
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post #2 of 8 (permalink) Old 09-28-2020, 09:48 AM
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Kh makes sense with ph on both sides. How are you measuring your hardness? How did you test/measure that specific of a kh and gh? I can guess that for myself but thatís because I use ro water that I remineralize to specific gh/kh. The only reason I can guess to the high gh in the tank is that your topping off with tap water instead of ro which just further concentrates the minerals (because they donít evaporate with the water). But then you said you change water regularly so that didnít make sense anymore. How often are you changing water and are you topping off in between? In the end both your gh and kh will be fine for most plants. Some demanding plants prefer soft water or theyíre so finicky the high calcium could throw off nutrient absorption which would hinder growth. But let your plants and fish tell you how your tank is going not the test kits.


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post #3 of 8 (permalink) Old 09-28-2020, 07:30 PM Thread Starter
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Thanks! I use the API test strips to measure everything, and then calculated out the dGH and dKH from the readings. I do weekly water changes, usually a good 20-25% or more, and rarely ever top off (I can think of a few times over the years when I had to delay a water change by a few days and so topped off, but it’s pretty rare). Our tap water in this area runs pretty soft, the local pet stores all have to add crushed coral to their ranks, so seeing a hardness reading like this really threw me. I immediately tested my tap water to see if something changed there, but as you can see, results showed it’s the same soft water it always was.
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post #4 of 8 (permalink) Old 09-28-2020, 09:18 PM
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Hmm. Are you using crushed coral or anything that would release minerals? If not, probably donít worry about it unless youíre seeing diminished growth. You could always get a tds meter to double check your test strips. I would also use the liquid dropper test kits by api to check kh/gh. The strips always have a is it this one or that one but the drops are just counting until the color changes very obviously.


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post #5 of 8 (permalink) Old 09-29-2020, 02:17 AM Thread Starter
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No crushed coral or anything, and I have the full API liquid test kit, I just use the strips at times for convenience and they have always matched the liquid test results anyway. I can’t say on plant growth yet, as nearly everything was just planted last week and all the plants are still adjusting. I’ll keep an eye and see if any plants start to struggle, or any fish show problems! Thanks!
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post #6 of 8 (permalink) Old 09-29-2020, 02:23 PM
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I would be a little concerned about a dGH reading that high, when the tap is so much lower. As you get into planted tanks, you will find that having too much of some nutrient can interfere with the uptake of another nutrient.

I'm guessing that something is adding a significant amount of [probably] calcium to your tank water. First thing that I would do would be to throw out the test strips. At best, they are misleading. Secondly, has your reagent API GH/KH kit expired (should be a date on the box)?

On the assumption that, in fact, you do have such a dramatic difference in your GH between tank and tap water, you may want to test things in your tank that may be adding either Ca or Mg. For example; the "regular old aquarium gravel" you mentioned is highly suspect. The Eco-Complete will raise GH (it has Ca and Mg in it), but this seems like a lot. Maybe others that have used Eco-Complete Planted can comment upon what is typical.

Get some drinking glasses or bowls and fill them with tap water, then add a few drops of lemon juice to them. Measure the dGH of this starting water for your baseline. Separate some Eco-Complete and your "regular old aquarium gravel" and put some of each in separate glasses. If you have any other hardscape/decorations, do the same with them. Stir the glasses a couple times each day. After a few days, compare the dGH of each sample to the baseline. This should reveal the culprit(s).

Incidentally, if you have high light, be very careful about the CO2 consistency. Make sure that you monitor the CO2 level in your tank and that it does not drift throughout the day.
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post #7 of 8 (permalink) Old 10-01-2020, 01:24 AM
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@Deanna is right on for finding a culprit.

Do you dose any fertilizer for your new plants? Anything with Ca and/or Mg will raise GH.

Also, 1 or 2 bps CO2 is not much in a 125 gallon tank.


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post #8 of 8 (permalink) Old 10-04-2020, 04:59 AM Thread Starter
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Yes, I listed my fertilizers in the original post. And in the CO2, like I said, I’m starting conservatively while monitoring levels and increasing as needed. I’m switching over to an in-line reactor this weekend, the diffuser just doesn’t give me the output I want.

So far, all fish and plants remain happy and healthy, so continuing to monitor and tweak where I can...
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