How to calculate the resulting kH after a water change ?

[Charles Silva]

Hello everyone

Is there an online calculator where can I input my tank volume, alkalinity, volume of new water and the new water alkalinity to get an estimatimation of the final alkalinity after a water change?

A friend with a 100 liters tank replaced 25% of the water and the alkalinity jumped from 8 to 12 dKH.
I'm curious to understand what would be de 25% alkalinity to raise the final tank water 4 dKH or if it was an error with her test.

Thanks
Charles Silva
Rio de Janeiro - Brazil

 

[Smokeshow]

Depending on the salt used it could jump 4dkh. What test kit are they using? I always test mine twice. Just to make sure. I use the red sea pro test kits. The one that uses the 1ml syringe.

 

[mdb_talon]

I don't know of a calculator that can do that online. The answer is around 32. Replace 25% of 8 dkh water with 32 dkh water would give you a total dkh around 14.

In other words testing error somewhere.

 

[mdb_talon]

Depending on the salt used it could jump 4dkh. What test kit are they using? I always test mine twice. Just to make sure. I use the red sea pro test kits. The one that uses the 1ml syringe.

Not really possible no matter what salt is being used. Either the original 8 dkh value was wrong or the resulting 14 dkh value was wrong(or both). It might be possible if a 100% change was done...but even then would need to be a salt above its advertised high end unless there are some mixes at 14 kh i dont know about.

 

[KStatefan]

75 liters X 8dKH + 25 liters X ?dKH = 100 liters x 12dKH

? = 24dKH

 

[Randy Holmes-Farley]

That required level of 24 dKH could possibly be attained if one used tap water to mix into a high alk salt mix.