Please help me calculate my GH given these water parameters: - The Planted Tank Forum
LinkBack Thread Tools Display Modes
post #1 of 2 (permalink) Old 10-23-2009, 02:17 PM Thread Starter
Planted Member
Join Date: Dec 2005
Location: New York, NY
Posts: 161
Please help me calculate my GH given these water parameters:

Please help me calculate my GH given these water parameters:

Iím embarrassed to say that after so many years in this hobby, I still canít figure out how to calculate my GH.

Here are my water parameters:
ē Calcium 10ppm
ē Magnesium 4ppm
ē Nitrate 9ppm
ē Potassium 16ppm

I know GH only factors in Calcium and Magnesium level. But, if thatís the case isnít that a poor indicator of true water quality? What if my Potassium level and Sulfate level are off the roof, like over 200ppm of each? Should GH and TDS reading be used in conjunction to get a true picture of your water parameter? I feel that GH is often over emphasized while TDS is neglected. BTW, my TDS meter reads 140 Ė does that sound about right given what I have above and using mostly RO/DI water or do I need to get it recalibrated?

I know KH is a function of GH and that the two are interconnected. So, If I have 2 degree of KH, does that mean I need that add that to my GH Ė Iím confused?

Lastly, can someone please confirm that 1 teaspoon of Calcium Carbonate raises approx. 1 degree of GH and 1 degree of KH to 25 gallon of water?

johnnyboy2476 is offline  
Sponsored Links
post #2 of 2 (permalink) Old 10-25-2009, 02:21 AM
I ♥ BBA!
sewingalot's Avatar
Join Date: Oct 2008
Location: WV
Posts: 12,768
Here is the formula for Mg:

GH(ppm*) - 2.5 x Calcium(ppm*) = Mg(ppm*)

Since you know your Ca and Mg, levels using the above formula, you can extract GH to have the following formula:

GH (ppm) = 4.1 x Mg (ppm) + 2.5 x Ca (ppm)

GH = 4.1 x 4 (ppm) + 2.5 x 10 (ppm)

GH = 16.4 + 25

GH = 41.4 (ppm)

GH = 2.3 (dGH)

*If you have the figures in degress, multiply by 17.86


The answers to your other questions are probably within the articles I sourced, but honestly I don't remember without reading all the details. Hope the calculation at least helps.

Without Algae, death of mankind would be inevitable.
sewingalot 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:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

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