Measuring gh with a tds tool

[joeyr188]

Hello i was wondering how much I would have to add/subtract from the amount I get from the tds to get the gh/kh

 

[Uberhoust]

I don't think that would be a valid measurement as it would depend on what is causing the conductivity within the water. You could have salt or some other ionic compound in the water which shows the TDS to go up, but it would not have any relationship with the KH in the water. Someone who uses these more might be able to help more.

 

[Byron]

I too do not think this is possible, since you cannot measure each substance contributing to the TDS. The following may explain more.

Total Dissolved Solids (TDS) is a measure of the combined content of all organic and inorganic substances contained in the water in molecular, ionized or micro-granular (colloidal sol) suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve the size of two micrometer.​

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TDS is connected to GH (general hardness) because like GH, TDS includes the calcium, magnesium and other “hard” mineral ions; these ions are what we measure with our GH test kits. But water hardness correctly considered is more than this; both GH and KH can affect hardness and TDS levels; however, the reverse is not necessarily true. Aquarium water can have a high TDS level but a low GH and KH (Jensen, 2009). The TDS for instance also includes sodium (salt) ions, chemical substances, etc. which are not reflected in the GH.​

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TDS is basically everything dissolved in the water: chlorine, chloramine, ammonia, phosphate, salt, hard minerals (GH), bicarbonates (KH), etc. And almost every substance added to the water will increase TDS: water conditioner, fish foods, plant fertilizers, calcareous substances, medications, water adjustment products, etc.​

 

[StevenF]

The problem will be low what DS is higher. Other times GH will be low what TDS is high. This means an adjust meant you come up with will sometimes be right or sometimes wrong. GH is mainly determined by Calcium and magnesium but TDS is everything