Adjusting kH and gH - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 11-29-2011, 01:51 PM Thread Starter
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Adjusting kH and gH

My tank has driftwood, eco-complete, plants and is cycled. I want to stock it with angels, rummynose, cories, and some sort of dwarf cichlid.

I was having an issue with pH swings- I guess because my gH was 4 and my kH was 2? So I put some crushed coral in my eheim, and now my pH has stabilized at 7.4 but my gH is now 8 and kH is 6.

Am I supposed to add or subtract the amount of crushed coral to fine tune the hardness? Normally my pH is 7.6 but I put the driftwood in after the crushed coral so I don't know what that will do to pH if I reduce hardness.

What should I do at this point? What would happen if I just took the coral out? Would my pH go wonky again if I did a big water change?

~June
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post #2 of 13 (permalink) Old 11-29-2011, 01:55 PM
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I have very hard water (high GH & KH) and am successfully keeping angels, cories, rummynose tetras, and many other fish.

If everything is stable with the coral as it is, I would just leave it.
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post #3 of 13 (permalink) Old 11-29-2011, 02:04 PM
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The GH doesn't directly effect pH, only the KH does. The crushed coral is adding to both.

What's the KH and GH of the water you use for water changes?
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post #4 of 13 (permalink) Old 11-29-2011, 02:11 PM Thread Starter
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gH is 4 and kH is 2 out of the tap. And pH is 7.6 as near as I can tell on the chart.

~June
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post #5 of 13 (permalink) Old 11-29-2011, 02:27 PM
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What's your target GH and KH? I wouldn't worry about pH at all unless it's swinging. Unless I'm introducing new fish to a tank I never test the pH.
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post #6 of 13 (permalink) Old 11-29-2011, 02:32 PM Thread Starter
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I'm thinking 3-6? I guess it's just the kH I am worried about. The pH dropped from 7.6 to 6.6 while I was cycling- is that anything to worry about, or does that just happen when cycling? I would prefer my pH to be a bit lower anyway.

~June
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post #7 of 13 (permalink) Old 11-29-2011, 02:42 PM
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If you only want to raise your KH then just add some baking soda to your water change water.

.2 tsp (that's "point" 2) of baking soda will raise your dKh by 1 point in 10 gallons.

I have at least 30 cories with some spawning at least every month and a breeding pair of angles in my tank and use 100% RO water. pH has always been on the low side but part of that is the CO2. Daily swing is near a full point.
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post #8 of 13 (permalink) Old 11-29-2011, 02:53 PM Thread Starter
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Thanks so much for your help! I'll ditch the crushed coral and add baking soda- .2 teaspoon (less than 1/4 teaspoon) per 10 gallons of change water to raise it to 3 deg. Or to make it a little easier I'll add a level 1/4 teasp.

Thanks again! This water chemistry stuff is SO confusing. No wonder I flunked organic chem in college

~June
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post #9 of 13 (permalink) Old 11-29-2011, 02:53 PM
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From what I've read, you want a KH of at least 4 in order to provide enough buffering to prevent PH swings. Depending on the substrate you use, it might provide the buffering required, which is why a lot of shrimp keepers use Aquasoil and don't bother adding anything to raise KH levels in RODI water. I believe Aquasoil buffers to around 6.5. Eco-Complete will buffer to 7.4-7.6, but that only lasts a few months depending on how often you do water changes and how hard your water is before it goes in the tank.

As to the coral, I don't remember off-hand what PH it will buffer to. I want to say 7.4, but could be wrong. Adding more coral won't change anything. If the water's PH drops below the set amount, it causes the coral to dissolve into the water, which causes the water's PH to rise. Once the PH reaches the "buffer level", it stops dissolving. Hope that makes sense, I'm trying to simplify the explanation, but I'm operating on limited sleep and not sure I'm doing too good a job of it.
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post #10 of 13 (permalink) Old 11-29-2011, 03:01 PM Thread Starter
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That does help explain things- thank you!

~June
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post #11 of 13 (permalink) Old 11-29-2011, 04:02 PM
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Geez! I wish I had you're water!

I use RO to have soft water.

My tanks are all generally kept at 4-6dGH and 2dKH. Exactly what your posting source water to be where you live.

Adding anything to a soil base or the filter that effects carbonate hardness is something I don't recommend doing. Once it's in place you have lost all control of to what level hardness will reach. Equilibrium with the material exposed to water circulation now controls and I didn't like that. Once it's in the substrate you can't remove it either. At least in the filter you can. I did a couple test tanks (10g) trying limestone and a couple other materials and just wasn't comfortable with the results.

Having made my water VERY soft then using it in tanks for several years now I feel safe saying 2dKH is enough buffer for stable pH even with CO2 injected systems. I use a purchased GH booster and Arm & Hammer baking soda for my RO water and all my tanks are stable and healthy from simple dirt tanks to injected and daily dosed high light tanks. Starting with the stripped water I mix for a target of 4dGH and 2dKH. Anywhere above 2dH I have had no problems. Even my oldest tank that closely follows D. Walstad's method (top off rather than water change) is kept in this way.

Baking soda is readily available and while many post both good and bad regarding it's use I'll say never a problem using it here. The results are very consistent on the hardness shift provided by BS.
Baking Soda = Arm & Hammer (generic may be OK) but I use A&H.
Using leveled TSP measurements this what I get with it.
1/8 tps/6.5gallons of water = 1dKH
1/4 tsp/13.g = 1dKH
1/2 tsp/26.g = 1dKH so you can figure your volume from there.

2dKH usually tests as 6.8-7pH
3dKH = 7.2-7.4pH
pH readings posted are water w/o CO2 injected.

pH during the day (photo period) will normally shift based on O2 levels so a change is normally seen. pH being effected by CO2 and O2 levels won't hurt the fish. Rapid shifts caused by changing the mineral content creates problems.


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post #12 of 13 (permalink) Old 11-29-2011, 04:58 PM
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Quote:
Originally Posted by RandomMan View Post
From what I've read, you want a KH of at least 4 in order to provide enough buffering to prevent PH swings. Depending on the substrate you use, it might provide the buffering required, which is why a lot of shrimp keepers use Aquasoil and don't bother adding anything to raise KH levels in RODI water. I believe Aquasoil buffers to around 6.5. Eco-Complete will buffer to 7.4-7.6, but that only lasts a few months depending on how often you do water changes and how hard your water is before it goes in the tank.

As to the coral, I don't remember off-hand what PH it will buffer to. I want to say 7.4, but could be wrong. Adding more coral won't change anything. If the water's PH drops below the set amount, it causes the coral to dissolve into the water, which causes the water's PH to rise. Once the PH reaches the "buffer level", it stops dissolving. Hope that makes sense, I'm trying to simplify the explanation, but I'm operating on limited sleep and not sure I'm doing too good a job of it.
It is pointless to change the KH of the tap water you use. As long as it is 1 dKH or higher you are preventing the pH from making wild swings with addition of CO2. (Actually, even lower KH will do the same, but 1 dKH is easy to read with a KH test.) KH and pH are over rated as something that needs to be monitored in a planted tank. Fast changes in either one can be a problem, but consistent low or high levels can only be a problem for certain plants or fish (when trying to breed them) or shrimp.

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post #13 of 13 (permalink) Old 11-29-2011, 05:09 PM Thread Starter
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LOL! I readily admit I don't know what I'm doing. I think I'm just going to take out the crushed coral and just monitor for awhile.

~June
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