# Can one convert TDS meter readings to GH or KH hardness?



## rusticitas

I am feeling a little bit dizzy after (re-re-re-)reading up on water chemistry this weekend. I acquired a nice TDS meter from a friend, and have been playing with it. What I cannot figure out, since I do not have any formal training in chemistry or anything that would seem to help is *IF* there is a way to take the readings from the TDS meter and convert that number to one that might tell me something about GH or KH.

Is there such a conversion? Thanks!

-J


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## gnatster

In a word, no. 

Reason being TDS meters measure all of the dissolved solids (minerals, salts or metals) and do not distinguish between them. There is an article in this months Reefkeeping about electronic Calcium measurements that you may want to read. I don't think the practice is doable for FW due to the lower Ca levels we keep.


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## Edward

No, that is not possible. 
TDS stands for Total Dissolved Solids. Every element conducts electricity in a different rate. For example kitchen salt does conduct quite well but Calcium carbonate doesn’t. So even though there is the same concentration the reading is not the same.
The TDS meter can be used as a tool to keep track of total water contamination. Some substrates dissolve so much that it causes stress on plants and fish. Other use is for RO unit, where we need to make sure the machine is still operating to the manufacturer specifications.

Edward


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## rusticitas

*In a word...*

In a word... dang. 

Ah, well, since the TDS meter was so easy to use, I'd been hoping I could just take note of the readings of tanks and do some conversion, rather than have to do the chemical test. No worries, thanks for the quick replies.


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## stvolkers

A friend is using a TDS to keep a base. The adds the ferts and watchs the results. This is someting like the PPS system from Edwards.


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