TDS Meter

mikejp67

Hi All,
As my amount of active tanks is now in the double digits, I bought a PH meter and a TDS meter.
PH meter works great.
TDS meter works great too but Im confused as to what Im reading. I want to be able to read my hardness in each tank. The readings are in PPM which I understand but some of my tanks are soft water (5dh) and Im reading apx 280ppm. Go to another tank...same water (5dh) and its 420ppm.
A live bearer tank with salt reading 1200ppm.
And, the unit is calibrated with solution so I know its reading perfect.
According to the package, 200ppm is considered very hard water yet my water is soft.
I understand ppm is a measurement of all dissolved solids not just minerals that make hard water.

Is anyone using one of these to measure hardness? If so, what are you reading and what ppm do you use for soft water...hard water...etc

Byron

As you've correctly mentioned, this instrument is measuring all TDS, which includes the mineral salts (calcium, magnesium, etc), common salt (sodium chloride), water conditioners, plant fertilizers if any, fish foods, and any other substances entering the water (additives, etc.).

The normal terms of soft or hard water generally refer to the hard mineral salts and the GH test kit measures these. But the TDS from the other mentioned substances also affect fish. Soft water fish are sensitive to these, so they should be as minimal as possible.

The difference in numbers between your tanks is indicative of the TDS some substances contribute. You mention "salt" for the livebearers, if this is common sodium chloride, this is best left out as it can be detrimental. Mineral salts from calcium, magnesium, potassium, etc are what the fish require as "hardness."

Byron.

mikejp67

When you refer to "mineral salts", would that be regular aquarium salt? If so, then if I use salt in my livebearer tanks then that alone will provide the hardness they need?

Byron

No. "Salt" as most of us use the term is referring only to sodium chloride, common table salt. "Aquarium salt" refers to either straight sodium salt or a mix of sodium and hard mineral salts. This is not safe for freshwater fish.

Salts that marine aquarists use are fine for marine fish or brackish water fish. These contain various mineral salts including sodium chloride. But this is not the best for any freshwater fish, due to the sodium. Rather than repeat the lengthy explanation, here's a link to my article on salt and its detrimental effect on fish:
Salt in the Freshwater Aquarium

The mineral salts sold for rift lake cichlids are fine, as these contain the hard mineral salts that these fish need. And livebearers can have these too. But a much less expensive method is to use a dolomite or crushed coral/aragonite blend of sand or gravel. This provides the necessary hard minerals without the sodium.

Byron.

mikejp67

Getting back to my original question.....Does anyone use a TDS meter?