Understanding gh/kh results

[NigelK8485]

I tested my gh/kh today using the API test. I lost my little instructions so looked them up, now...to do this test do I just read the chart separately for both GH and KH?

My GH took 7 drops to change color, which would be 125.3 ppm.
The KH took 3 drops, or 53.7 ppm.

Correct?

If I'm planning on running pressurized CO2 should I increase the KH? I used to keep a bag of crushed coral in one of my canisters to buffer against pH drops. I ended up removing it for basically no reason, I added more biological media in its place. Should I look at introducing the crushed coral again to increase the KH? PH is at 7.6.


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[Brookster123]

You're good, not optimal but not low enough to justify tampering..

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[NigelK8485]

You're good, not optimal but not low enough to justify tampering..

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Fair enough, thanks.


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[ScotJudd]

Ordinarily a Kh of 3 would help prevent an acid crash. Personally I like to keep my Kh at about 6 as I'm injecting Co2. Coral would help but I don't like to leave it to chance and add a little Bicarb of soda to each bucket of new water. My Kh is almost zero from the tap and Co2 injection dropped the Ph. Even at Kh 6 it falls a little each day (about 0.3) and goes back up at night. 2.5ml of bicarb raises 10l of water by about 6 Kh.
I understand Brookster saying you are on the low side but OK, however, with Co2 I would say your Kh is too low. A lot will depend on the amount of Co2 you inject.
In any case start slow with Co2 and increase bubble count a little each day until you reach your optimum level. Water volume, Kh, plants and lighting all play a part so there is no exact bubble count to advise.
I have had fantastic results with my Co2 but treat it cautiously, observing the drop tester, Ph and fish behaviour.



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[NigelK8485]

Ordinarily a Kh of 3 would help prevent an acid crash. Personally I like to keep my Kh at about 6 as I'm injecting Co2. Coral would help but I don't like to leave it to chance and add a little Bicarb of soda to each bucket of new water. My Kh is almost zero from the tap and Co2 injection dropped the Ph. Even at Kh 6 it falls a little each day (about 0.3) and goes back up at night. 2.5ml of bicarb raises 10l of water by about 6 Kh.
I understand Brookster saying you are on the low side but OK, however, with Co2 I would say your Kh is too low. A lot will depend on the amount of Co2 you inject.
In any case start slow with Co2 and increase bubble count a little each day until you reach your optimum level. Water volume, Kh, plants and lighting all play a part so there is no exact bubble count to advise.
I have had fantastic results with my Co2 but treat it cautiously, observing the drop tester, Ph and fish behaviour.



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What about coral would be leaving it to chance?


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[RightTurnClyde]

I don't run CO2, but I also recently got the GH/KH API test. I have a result of about 4 dKH out of my tap, but I found that if I test my tank water later in the week, it drops to 2 dKH before it's water change time again. This makes sense if you realize what the carbonates in the water actually do, which is absorb and neutralize acids. Once they do their job, they are used up.

I happen to have a jar of Seachem's Alkaline Buffer (you could use Baking Soda to the same effect.) I added 1 heaping teaspoon to my 29 gallon tank today after my water change. (The recommended dose is 1 teaspoon per 20 gallons to raise the KH by 2.4 dKH.) I tested it again after letting the water circulate for about an hour. It had bumped up my KH to 6 dKH, but did not noticeably change my pH from it's usual 7.8. I'm going to keep doing this in the future, for peace of mind, even though I've never seen my pH change. I read that if your KH is at 3 dKH or below, you might want to start worrying about pH shifts.

 

[ScotJudd]

Kh is also known as temporary hardness for good reason, especially if injecting Co2. Leave a tank long enough and it will run out of carbonates. Running a tank at Kh 3 and doing regular water changes with a source water of about Kh3 is probably workable. But what about those times when circumstances get in the way of this regular routine, eg holidays or illness. Having a robust Kh gives you leeway to confidently leave the tank running without worrying about Ph crashes.
Crushed coral is an option that I've never used but have heard it can help stabilise Kh and avoid Ph crashes.


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