kh and gh confusion - The Planted Tank Forum
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 11-03-2014, 02:03 AM Thread Starter
Algae Grower
Whitesage's Avatar
PTrader: (0/0%)
Join Date: Mar 2014
Location: Sardis, Ms
Posts: 56
Question kh and gh confusion

my GH is very low 1 or 2 dgh my KH is high 8 or 9 in an aged tank water 14 right out of the tap. So many people interchange gh and kh and I'm really tired of being confused. What I understand is the DKH at 8 or 9 with co2 is good. I use DIY co2 the John LeVasseur set up. The ph added with the peat moss is running 6.8 to 7.0. I'm getting not cheap Angels from AngelsUSA soon I want to make sure I don't end up with swings and dead fish.
Whitesage is offline  
Sponsored Links
post #2 of 8 (permalink) Old 11-04-2014, 01:07 AM
Planted Tank Enthusiast
JoeRoun's Avatar
PTrader: (0/0%)
Join Date: Dec 2009
Location: Surprise, AZ
Posts: 634
Smile Sounds Exciting


General (also called permanent) hardness (GH) and carbonate (also called temporary) hardness (KH) really have little to do with one another.

Your water is just fine.

The KH is the buffer and running just under pH 7 is great.

Remember Angelfish really like large water changes.

Have fun, after all this isn’t golf…


If your Guru tells you otherwise and you are true believer that is okay I will not argue the point.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

I pretty much limit what I say to things that anyone can easily verify from recognized references or by direct observation. If it is my opinion I say so.

JoeRoun is offline  
post #3 of 8 (permalink) Old 11-05-2014, 07:37 PM
Planted Tank Guru
klibs's Avatar
PTrader: (29/100%)
Join Date: May 2014
Location: NH
Posts: 3,325
You will be fine. Just acclimate them slowly (as always) and I doubt you will have issues. Angels are pretty hardy.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
klibs is offline  
post #4 of 8 (permalink) Old 11-05-2014, 08:07 PM
Planted Tank Guru
PTrader: (3/100%)
Join Date: Aug 2014
Location: Maryland, USA
Posts: 2,339
+1 on JoeRoun's bit on KH...

To add a bit to it and illustrate the differences.

GH is mostly a measure of the amount of calcium and magnesium in the water. There are other minerals, but these are your big influences here. It has nothing to do with pH, and more to do with the mineral content of the water.

KH, as JoeRoun pointed out, is a measure of carbonate in the water. Carbonates buffer the pH of the water and stabilize it against acids. It's another way of expressing total alkalinity in water, although usually folks express KH in German degrees and total alkalinity in ppm.

People often confuse them, and sometimes imply they are related.

They're only related to the extent that the KH and GH in many natural water supplies is from calcium carbonate and/or magnesium carbonate, caused by the water flowing through limestone or dolomite in the ground. Since these rocks contain both calcium/magnesium and carbonate, they raise both KH and GH at the same time. Most natural "hard water" is high in both GH and KH. Of course it is always possible for water to encounter something like gypsum (calcium sulfate) in nature and end up high GH/low KH...

In your case the water has a lot of carbonate, but not much calcium or magnesium.. this suggests something like sodium carbonate was added to the water at the water treatment plant, or it went through an ion-exchange water softener at your home...

Note - I'm not suggesting this is good or bad, just explaining the mechanics of how this likely happened to the water... I strongly defer to others more experienced with fish than I here.

Last edited by mattinmd; 11-05-2014 at 08:14 PM. Reason: added note about good vs bad.
mattinmd is offline  
post #5 of 8 (permalink) Old 11-06-2014, 06:24 AM
Algae Grower
PTrader: (0/0%)
Join Date: Oct 2014
Location: Australia
Posts: 19
Hi Whitesage.

I'm glad you posted. It is unusual for GH to be 1-2DGH, while you have 8-9DKH in tank and 14DKH in tap (or indeed) change water. The CO2 is reducing the DKH. And DKH is fine as JoeRoun, Klibs and Mattinmd have mentioned.

Mattinmd's comments are well founded. KH is not a part of fish health. It is, in the simplest terms, just for the bicarbonates (in a freshwater tank) that keep PH stable.

In introducing new fish I believe it is important to find out what are the PH levels of the water that they are coming from. PH should be within say .4 to even 1, of their current home and your tank (their new home). If the PH difference is close to 1 or even more, a longer acclimation process will be needed.

I actually believe that GH is more important than PH. GH level is important for best osmotic process's of the individual fish. Angel's can live in 1-15 DGH according to aquadvisor, but if the Angel you buy has been raised in a GH of say 7DGH the acclimation process when the fish is added will be a tough one. Easier to raise the GH to suit the new inhabitant, but also being mindful of the GH needs of your other fish in the tank.

That said, I wouldn't muck around with PH. It can be done, but it takes a lot of effort.

Find out the new inhabitants current water parameters for PH and GH, and post your tanks PH, and I will be able to help more, if indeed help is needed.
WaterKeeper is offline  
post #6 of 8 (permalink) Old 11-06-2014, 12:51 PM
Planted Tank Guru
PTrader: (0/0%)
Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721
Start with GH for the fish.
Research what your fish thrive in.
Also, get to know the water the fish have been living in. Test the water in the bag for GH, KH, TDS, pH.

Set up a quarantine tank with that GH.
I set the KH pretty close to the GH, unless tests show it should be different.
If the fish is a black water fish, then add peat moss to the filter for the organic acids.
I also test the TDS of the water in the bag. There are some stores with such a high TDS (mostly from salt) that I something think I should quarantine fish from them in my brackish water tank!

Fish will be in quarantine for a month, and during that month I do several water changes which gradually acclimates the fish to the parameters of the main tank. This is set up to suit the fishes' requirements.
Diana is offline  
post #7 of 8 (permalink) Old 11-06-2014, 03:12 PM Thread Starter
Algae Grower
Whitesage's Avatar
PTrader: (0/0%)
Join Date: Mar 2014
Location: Sardis, Ms
Posts: 56
Strangely enough the water params in the bag are very close to the water params of my tank. I don't know if that's what they raise them in but they've been in there for 24hrs so it shouldn't be a big change for them. I'm doing a slow drip about 2/sec I'll let the water double in the bucket before I add them to the tank. I never use artificial means to alter water chemistry. It's just too chancy. Instead I fill up a 40g plastic tub and let it sit, run some air and maybe a heater in winter. About the only thing I do is add a tiny amount of peat moss. BTW they are absolutely GORGEOUS! Philippine Blue Silvers with 1 Smokey and 1 platinum that may turn out to be a ghost. Nice job AngelfishUSA .
Whitesage is offline  
post #8 of 8 (permalink) Old 11-09-2014, 04:46 AM
Algae Grower
PTrader: (0/0%)
Join Date: Oct 2014
Location: Australia
Posts: 19
Hi Whitesage

Good to hear that parameters in fish delivery bag are the same as tank. And glad that the new fish are the colours that you hoped for.
WaterKeeper is offline  


Quick Reply

Register Now

In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome