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Discussion Starter · #1 ·
I just received my water TDS meter, it seems to be working fine.

RODI - 20ppm
Planted tank - 250ppm
tap - around 220ppm
Shrimp tank -220ppm

My question is this. I am trying to achieve a GH hardness of 5 degrees.
I am using an API GH KH tester.
The water in my shrimp tank is registering on the meter as 220ppm TDS, brought it down from near 600ppm by rodi dilution.
The GH level reading from my API test kit has the water turning green at 4 drops, meaning 4 degrees GH.

I checked on the instructions per said test kit and it states the following:
0º - 3º (0-50 ppm)
3º - 6º (50-100 ppm)
6º - 11º (100-200 ppm)
8º - 12º (140-200 ppm)
11º - 22º (200-400 ppm)

According to the API test kit, the water at 5 degrees GH should be between 50-100ppm?

But i am reading 200ppm+ at 4 degrees hardness.
 

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GH and KH tests register different things and the combined total is you're basic mineral and carbonate hardness. 17.9 ppm is 1 German degree on either test.
TDS registers anything in the water column that conducts the small electrical charge produced by the meter "conductivity" this will always be slightly or notability higher than the GH/KH tests because organic and 'other' compounds help conduct the charge measured.
My use of TDS measurements is by knowing my baseline reading on clean water then later seeing the shift upward caused by dosing and other additions to the tank. Reviewing these recorded shifts I have an idea how much change there is to my water quality. Very basic in how I utilize the tool.

HTH
 

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Discussion Starter · #7 ·
Thank you everybody! I appreciate the input. I had a mini fiasco with raising GH but crisis averted and the sun is shining! I did read that thread regarding Tds and gh and found it to be very informative. I surely have learned much since July!

Wkndracer, like you I will be using my Tds meter to gauge the water I'm adding into the tank dissolving gh boosters into rodi.
 
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