Water Hardness

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YnotFish
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Hi all :swim:

The Missus has a shrimp nano cube type aquarium and the lfs sold us a super-duper electronic hardness measuring thingy.
The guy at the lfs (who seems pretty knowledgeable) advised us to use the us/cm (micro Siemens per cm) setting, not the ppm (parts per million) and that, for red cherry shrimps, we should be aiming at around 200 us/cm.
Our initial measurement was around the 500 mark (which probably explains why we haven't seen the cherries for a while - we are going to wait until we have the tank stable before getting any more), so we took out all the rocks and made a couple of 30% water changes with Osmosis water that we measured at 35 us/cm. Now we have the tank down to 282. We will continue the water changes and see if it drops down further.
Questions:
1. how does this micro Siemens/cm measurement relate to GH / KH? :hmm:
2. is this super-soft water going to be ok for our Endler Guppies?
Cheers!
YnotFish :cool:
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fr499y
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cherry shrimp should be fine in hard water, but crystals need it softer. Endlers also need hard water. If you have the two in the same tank then I wouldn't be suprised if the endlers have/tried to eat the shrimp which is why they are hiding or missing.

275ppm is 15.4 gdH which is hard, but imo perfect for cherries and endlers.
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YnotFish
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um... I am measuring 143 ppm, or 282 us/cm.
Also I wrote "red cherry" but I actually have "red crystal" shrimp, so they prefer softer water?
Is there a handy conversion table somewhere?
Cheers!
YnotFish :cool:
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fr499y
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yes 1 mo, I'll add it to the resources page.
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YnotFish
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Thanks for that :]

So now I am still confused by this stuff :crazy:
It has two settings, one that measures "TDS in ppm" and one that measures "electrical conductivity in us/cm".
The ppm value seems to be half of the ec value?
Anyway, according to "the Internet" the red crystals would need the following parameters:
GH 4-6
KH 0-1
TDS 140-160

so, is TDS not the same as GH? :mindblown:
I think I need "Aquarium Water Hardness for Dummies"...
Cheers!
YnotFish :cool:
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fr499y
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no TDS = total disolved solids including calcium and magnesium which is whats measured in hardness.
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Vale!
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Oooh! A question that I can help with! Whether I can make my answer understandable is an entirely different thing ..


Pure water doesn't conduct electricity : it would read "0 μS/cm" on your conductivity meter machine.

To get it to start conducting electricity it needs to have salts dissolved in it. When salts dissolve they dissociate into positive and negative electrically-charged ions (known as cations and anions respectively). Thus, for example, calcium carbonate dissociates into positively-charged calcium cations and negatively-charged carbonate anions. Again, calcium nitrate dissociates into calcium cations and nitrate anions.

In our context, the cations of some salts carry double positive charges rather than single ones : both calcium (Ca++) and magnesium (Mg++) do this, and are 'matched' in solution by the corresponding number of negative anions. Other salts carry singly-charged anions ; so, for example, a potassium chloride molecule dissociates into K+ and Cl- in solution.

The amount of dissolved salts and their ionic characteristics (how many plus or minus charges they carry) dictates how well they conduct electricity and therefore what a conductivity meter will report.

You stick your machine into a random bowl of water and it reports (say) 500 μS/cm. You now know that there are salts dissolved in it, but you don't know what they are or how much of each (proportionally) is involved. So you can't tell how much of the conductivity reported is because of calcium carbonate. You need a GH test to resolve that.

However in most situations (certainly in mine) it's the overall ionic strength - a conductivity meter reading - which is significant. From a fishy-health point of view it's important to ensure, as far as is reasonably possible, that the water in which we plonk a fish has roughly the same ionic strength as the water in which its ancestors evolved. I don't know how far that principle extends to shrimp. In my case, should such info be of any value to you, I try to keep my tanks' water below 100μS/cm and both cherry shrimp and Amano shrimp do OK in it. I do add a bit of calcium (~3.5 grams in a 210-litre water butt of RO/DI water) and magnesium (~1.5 grams) but that's not enough for a standard GH test to resolve.


Bonus info #1: I believe that a conductivity meter operates by measuring resistance to current but somehow converts that to conductivity!

Bonus info #2 : A few on the Forum own TDS (Total Dissolved Solids) meters. These are actually conductivity meters, but with a built-in calculation based on the assumption that the water being tested possesses a 'typical' mix of dissolved salts. The built-in factor is usually something like 0.6, so a conductivity meter reading of 500μS/cm would read 300mg/l (or 300ppm) TDS. Higher-end TDS meters offer the facility to adjust the built-in factor if you happen to know exactly what salts are dissolved in water that's being tested!


Edit: to acknowledge M's interposed post(s)!
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fr499y
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@Vale! feel free to check the calculator and let me know if any of the conversions are wrong!
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