# Tds



## rickwaines (Jan 2, 2011)

Can anyone point me in the direction of some good reading helping me understand the relationship between TDS, GH and KH?

Thanks!


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## ilam (Apr 28, 2011)

I don't think there is a definitive relationship between TDS and GH and KH. If you increase your GH or KH, your TDS will go up. The TDS is only a measure of dissolved solids in the water which includes minerals (which affect hardness), dissolved organics and other contaminants. Depending on where you get your tap water, it will simply be different. If I want to raise my GH to 4 using seachem replenish, i will get a different TDS measurement than if i used seachem equilibrium to get a GH of 4.


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## Fish rookie (May 21, 2012)

sorry duplicated post.


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## Fish rookie (May 21, 2012)

Think--but I could be wrong--if you increase GH/KH your TDS should go up since you are dissolving more minerals into the water. But just because you have a high TDS does not mean you have higer GH/KH/PH.
Usually KH goes hand in hand with PH so a high KH usually leads to a higer PH and a higher TDS. However, if you have a lot of organic waste your PH might go down since de-nitrifying lowers KH. Believe the presence of some minerals also affect KH/GH such as phosphate.
Some GH measuering kit only measures the presence of Ca, Mg but not necessarily in its ion form so just because you have a high concentration of Ca and Mg (i.e. high TDS and may be high GH) does not always mean you really have what the fish need. If the ions are depleted then your fish can still be unhealthy.The amount fo Ca and Mg ions would greatly increase after a water change rather than jst topping up, and that is important. TDS in this case as it does not show you whether the minerals are in their ions form or depleted. 

But I could be wrong as is usually the case so take what I say with a grain of salt pleae. LOL


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## rickwaines (Jan 2, 2011)

The Importance of Total Dissolved Solids in the Freshwater Aquarium - plecoplanet Forums

this is helpfull too. Thank all. Knew I shoulda gone to more chem classes in high school.


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## 2wheelsx2 (Apr 21, 2010)

Don't get too overly wrapped up with TDS because the meters out there read conductivity to determine TDS and use a calibration factor. So lots of things can affect that reading. For instance, I can get a TDS reading in the 100's outside of the water inside the canopy, which is totally meaningless.


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## rickwaines (Jan 2, 2011)

ohhhh great.


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## neven (May 15, 2010)

for the tanks i dont ei dose (meaning weekly water change not needed) i use my TDS probe to see when water changes are necessary. I know what my buffered water TDS is that i put in the tank, so any number higher is a resultant of Nitrates and Dissolved organics. Also if things go wrong with my water, it saves me from measuring hardness. I normally change water, but sometimes i get lazy, so a quick probe check puts my mind at ease


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## gsneufeld (Jan 28, 2012)

Fish rookie said:


> But I could be wrong as is usually the case so take what I say with a grain of salt pleae. LOL


i get it! *rolls on floor laughing* yeah first post got it I think, all the dissolved minerals and salts in your tap water plus whatever you add to stabilize your PH.


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## Fish rookie (May 21, 2012)

gsneufeld said:


> i get it! *rolls on floor laughing* yeah first post got it I think, all the dissolved minerals and salts in your tap water plus whatever you add to stabilize your PH.


LOL, yeah, a grain of salt and some equalibrium and stability...LOL


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## kelownaguy (Jan 1, 2011)

rickwaines said:


> ohhhh great.


Not to worry.

Conductivity mesurements taken w/a TDS meter are more significant for fishkeeping purposes than the "true" TDS obtained by evaporating the water and weighing the remaining solids anyhow.


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## kelownaguy (Jan 1, 2011)

neven said:


> for the tanks i dont ei dose (meaning weekly water change not needed) i use my TDS probe to see when water changes are necessary. I know what my buffered water TDS is that i put in the tank, so any number higher is a resultant of Nitrates and Dissolved organics. Also if things go wrong with my water, it saves me from measuring hardness. I normally change water, but sometimes i get lazy, so a quick probe check puts my mind at ease


A higher number on your TDS/conductivity meter is not the result of Dissolved organics.
They do not register on a conductivity/TDS meter.
Increasing TDS readings are due to the accumulation of inorganic ions like nitrates ,phosphates,sulfates,chlorides,sodium,potassium etc. from feeding/fertilizing and evaporation.

I also use the tds meter to help time water changes.


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