Questions about my GH and KH readings - The Planted Tank Forum
 
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post #1 of 11 (permalink) Old 03-05-2014, 02:57 PM Thread Starter
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Question Questions about my GH and KH readings

My 5 gallon tank just finished a fishless cycle (I feel rather proud of myself for sticking it out).

Here are the current readings.

Ammonia 0ppm (after being brought up to 3ppm yesterday)

Nitrites .25ppm (they came down really quickly about 2 days ago)

ph: 7.4

Nitrates had creeped on up there, so I did a 25% water change. I will test again this evening and see if I need to do another one.

GH: 14 - which really surprised me as it was 7 on the 12th of last month.

KH: 3 - which also surprised me since it was 9 on the 12th of last month.


Could the GH and KH fluctuations be due to the cycle? I do have a piece of sandstone in the tank, could that be it?


Are these readings in anyway bad? I plan on keeping a betta and a few amano shrimp in the tank.
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post #2 of 11 (permalink) Old 03-05-2014, 10:25 PM
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Please retest GH and KH so we can see which of your other tests they are closer to. Also please test your cold tap water for GH and KH, and pH while you're at it to see if there's a difference. A lower GH in the tap water would indicate something being added to the water in the tank, like from a rock or the substrate. What is the substrate, btw?

Oh, I don't know if sandstone is particularly basic. A rock containing Calcium would be more likely to contribute to the GH. To be sure, and if someone knows about sandstone please chime in, take out the sandstone rock, dry it off, and pour a few drops of vinegar (acetic acid) on it - if it fizzes, it's no good.

I don't think the fluctuations have anything to do with the cycle. A GH of 14 is pretty hard water - 7 is much better. KH of 3 is as low as you can go without risking pH swings. My KH is about 3.

GH and KH tests can be hard to measure. Use good light and a piece of white paper to do the tests and see the colors. Let's see how new tests come out.

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post #3 of 11 (permalink) Old 03-05-2014, 10:30 PM
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I'd bet the GH fluctuations are probably due to the sandstone rock you have in the tank, though they could be due to topping up the tank to replace evaporated water if you are doing that. Most rocks in the Knoxville area are sedimentary, but a good number of them looked to be made from some sort of calcium deposit.

By the way i like your avatar it makes me smile. Also, Knoxville is quite a nice area, I was just down there last week at LMU-DCOM, I may be down there in the fall if all goes well.
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post #4 of 11 (permalink) Old 03-05-2014, 11:04 PM Thread Starter
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Django, I will test the tap and tank separately tomorrow. I am using Caribsea Aquamax for the substrate.

I stopped by our LFS today (where I bought the piece of sandstone). They said it shouldn't have affected the water hardness to that extent.
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post #5 of 11 (permalink) Old 03-05-2014, 11:08 PM
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LFS don't know 1/2 the things people think they do. The people they hire are almost always normal kids out of high school with no special training or interest in fish.

Test the rock. Take white vinegar or another acid and drip it on the rock. If the rock fizzes or discolors then it has calcium or magnesium in it and it is changing your water chemistry. Be sure to scratch the rock first before you add the acid to it so you scratch off any protective oxidation layer that might be on the rock.
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post #6 of 11 (permalink) Old 03-05-2014, 11:12 PM Thread Starter
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Thanks! I'll do that after dinner.

Quote:
Originally Posted by Zapins View Post
LFS don't know 1/2 the things people think they do. The people they hire are almost always normal kids out of high school with no special training or interest in fish.

Test the rock. Take white vinegar or another acid and drip it on the rock. If the rock fizzes or discolors then it has calcium or magnesium in it and it is changing your water chemistry. Be sure to scratch the rock first before you add the acid to it so you scratch off any protective oxidation layer that might be on the rock.
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post #7 of 11 (permalink) Old 03-05-2014, 11:57 PM
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Quote:
Originally Posted by Niyona View Post
I am using Caribsea Aquamax for the substrate.
Could it be FloraMax?

FloraMax is high in calcium.

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post #8 of 11 (permalink) Old 03-06-2014, 01:10 AM
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Many rocks and substrates will increase GH, and KH. The most likely culprit is calcium carbonate. It's a substance that is often found in many of the decorative rocks we use.

Other things can raise GH including Ca,Mg(co3)2 (dolomite) which is in rocks too.

kH going down during a cycle is not unheard of. Bacteria need carbonate to reduce ammonia and nitrite. Since the tank is new lots of bacteria are forming and using kH as their source of carbon.
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post #9 of 11 (permalink) Old 03-06-2014, 04:39 AM
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If your tap water has GH and KH closer to what you want for the fish, then do a really big water change (like 90%) and see what that does, and how long it stays stable.

If you have some of the same materials you used left over from setting up the tank test these in a jar of water. Put a handful of substrate in a jar of water, put a chunk of sandstone in another jar, and if there is anything else you are adding to the water put some of that in other jars.
Test GH, KH, pH and TDS before you start, then every few days for a week or two, or until you see a change. If the tests run out a couple of weeks with no change, then you can assume that item is neutral as far as the aquarium is concerned.
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post #10 of 11 (permalink) Old 03-06-2014, 11:32 PM
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I could see the carbonates (KH) getting exhausted by buffering the water when acids are produced from decomposition and tannin leaching and such. But if it were coming from the rock, I would think it would be replaced about as quickly as it's used up.

No real clue on why the GH increased though... possibly the sandstone has a carbonate matrix/cement, and that is leaching out, but the KH is getting buffered by acids?
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post #11 of 11 (permalink) Old 03-07-2014, 09:14 PM Thread Starter
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Alright, I have done a few 25% water changes over the last couple of days. I also tested my tap water.

After water changes my GH went down to 11 and my KH rose to 5.

My tap water has a GH of 8 and a KH of 7.


I'm going to test daily for the next few days and try to keep track of changes.
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