How do you check your water hardness/sofness

[Jholden]

What test or meter or should I be using to test my water hardness/softness.

I was looking into buying a EC/TDS meter till I found out they dont really measure carbonates? Which would in theory make the water harder? I'm a bit confused. What do you use personaly? I've been using simple API kh and gh reagent test kits but I'd like to get some type of meter for the purpose of practicality.

thanks much
-Jay

 

[jmtrops]

I use a conductivity meter. we have a guy around here that sells a decent one for like $42. I dont worry about any other parameters just conductivity.

Jim

 

[dw1305]

Hi all,
Jay, you are right, but jmtrops "conductivity meter" is a good suggestion.

Most Apistogramma spp. come from water which is very low in all salts, and not just calcium carbonate, so we need water with both low conductivity, and low hardness (probably R.O. or rainwater, unless you have very pure tap water). Pure H20 is actually not a conductor of electricity, it is only as solutions that it conducts electricity. Our tank water is nearly always a dilute solution of various salts, and put simply the more salts dissolved the greater the electrical conductivity.

The important fact is that all salts contribute to the conductivity, but only calcium and magnesium carbonates (Ca and Mg2+ ) contribute to the hardness. As an example water "softener" which works by exchanging sodium Na+ for Ca2+ (one where you use salt (NaCl) in it) will reduce hardness, but not conductivity.

pH is another related variable, I won't go into the details here but as a measurement pH isn't very useful on its own.

As an example the water coming out of our de-ioniser has a conductivity of 2 - 3 microS, meaning it is almost pure H2O and only conducts electricity very poorly, the pH should theoretically be pH7, but will probably be about pH6, due to the small amount of atmospheric CO2 that has gone into solution (and formed carbonic acid), the pH will also be very unstable (we have no "buffering"), and any addition of very dilute alkali will send the pH up, to pH 9 or 10, or addition of weak acid down to pH 2 or 3. The water out of the distillation unit will be 20 - 30 microS (unit needs a clean), our rainwater 120 microS (it should be much lower, but it has picked up calcium carbonate dust from the atmosphere as it is all limestone here). Our tap water (from a limestone aquifer) is a fairly stable pH 7.8 and about 650 microS., but it is strongly buffered, and we would need to add a lot of acid to reduce the pH.

If we get into the realms of the African Rift Lakes or the Sea, we are talking about water which is more strongly buffered again.

I can't think of a good every day example, so I'll use instant Coffee as my "alkali salt" and sugar as my "acid", and assume my water really is just H2O.

I start with water, and I add some coffee to the water, but it is too bitter, so I add some sugar, and it is now too sweet, so I add some more coffee, and now it is just right, but what I have is black coffee, not water any more.
Water with high hardness or conductivity all ready has the "coffee" added, we can add sugar (and make coffee), but what we really need to do is to remove the coffee, and get back to plain water.

Hope that helps

cheers Darrel

Have a look at this posting on "the krib" <http://www.thekrib.com/Plants/CO2/hardness-larryfrank.html>.

As this can be quite a confusing subject, with loads of different terms and units, I've shameless pinched parts of the above link to post to another forum, and I've pasted this below.

.....TDS
is total dissolved solids, and hardness is a measure of dissolved multivalent minerals (Ca2+, Mg2+) in the water (multivalent just means there is a number in front of the +, e.g. Ca2+).

To convert TDS to conductivity in micro S.
64 ppm TDS = conductivity of 100 micro S, and 100 ppm TDS = 156 micro S.

There are 2 types of hardness "temporary" where boiling will remove them - carbonates, usually calcium or magnesium, and "permanent" which can't be removed by boiling - sulph(f)ates, chlorides e.g. magnesium sulphate ("Epsom salts").

In the UK hardness is most usually a measure of the calcium carbonate (the lime(stone), chalk or scale) content. The equilibrium reaction is:

CaCO3(solid) + H2CO3(aq. in solution) ⇋ Ca2+(aq) + 2HCO3-(aq) (exactly same for Mg2+ as well, so both Ca and Mg are usually added together and expressed just as calcium)

As you heat the water CO2 becomes less soluble (it's not in the equation as CO2, but bicarbonate is - 2 x HCO3-) which moves the equation from right to left (less CO2 means less bicarbonate ions HCO3- to balance the Ca2+ ions), Ca2+ can't remain in solution and are precipitated out as the "scale" (CaCO3) in your kettle, immersion heater etc.

Ion exchange resins (water softener) can remove both types of hardness by exchanging sodium (Na+) or potassium (K+) for the calcium and magnesium (but you would still have high conductivity and TDS).

Units
Parts per million (ppm) is the same as milligrams per litre (1000 cm3 in a litre, which for water weighs 1000g (a kilogram), 1000 milligrams in 1cm3 which weighs 1 gram).

Parts per billion (ppb) is micrograms per litre (1000 micrograms to the milligram).

mmol/L (millimoles per litre)
One millimole of calcium (either Ca2+ or CaCO3) per litre of water corresponds to a hardness of 100 ppm or 5.61 dGH, since the molar mass of calcium carbonate is 100g/mol.

(Ca has a RAM of 40, C = 12 and O = 16, CaCO3 = 40 + 12 + 48(16 x 3) = 100).

100g in 1 litre is a molar solution of calcium carbonate (40% Ca), and 0.1g per litre a millimolar solution.

General degrees of hardness is the same as German degrees (dGH).

1 dGH is "One degree German" and defined as 10 milligrams of calcium oxide (CaO) per litre of water. This is equivalent to 17.85 milligrams of calcium carbonate per litre of water, or 17.85 ppm. (look up American, Clark, French degrees etc. on Wikipedia for a conversion).

As an example my tap water (Corsham, Wilts - SN13 9AR) is:

Calcium (milligrams per litre) 119 (298 x 40% = 119)
Calcium carbonate (milligrams per litre) 298
Degrees German (ºdH) 16.7 (16.7 x 17.85 = 298)
Degrees French (ºf) 30
Degrees Clark 21
Sodium (milligrams per litre) 22
Conductivity 615 micro S(iemens)

Descriptions of hardness correspond roughly with these ranges of mineral (Ca, Mg) concentrations: (pinched straight from Wikipedia)

* Very soft: 0-70 ppm, 0-4 dGH
* Soft: 70-140 ppm, 4-8 dGH
* Slightly hard: 140-210 ppm, 8-12 dGH
* Moderately hard: 210-320 ppm, 12-18 dGH
* Hard: 320-530 ppm, 18-30 dGH
* Very hard >530 ppm, >30 dGH

Making my water officially "moderately hard". However I've tested my water a couple of times and the conductivity was about 800 microS, suggesting that the value may be quite variable around the average figure given.....

 

[jmtrops]

Everyone does different things when it comes to water parameters but I like to keep it as simple as I can. It also depends on what kind of fish you are keeping and if you are trying to apawn them. I use three basic water types in my tanks. One for rift lake cichlids 600-700 us, one for central and some south american which I use tap water 400 us and one for my soft water fish 10 to 1 RO/tap 80-100 us. The only one I add any chemicals to is the rift lake water. I add some salts and buffer to get it up into that range. For me pH is only important for one reason and that is the affect it has on amonia toxicity. Since my filters work I have no amonia in my tank so I never check pH or care what it is. When I move fish from one tank to another I check conductivity to make sure they are close so it doesnt stress the fish or kill them from changes in osmotic pressure. A lot of these soft water fish will spawn regularly in my tap water. When I was importing apistos from peru we would keep them in our tap water and after being in a holding tank for a week many of them would spawn. Of coarse there are always ones that need those special conditions so you should know what conditions your fish need and adjust what you need to measure and adjust to that.

Jim

 

[Jholden]

thanks for the replies guys.. very insightful. I'm keeping Apisto's using an RO unit for my water. So I'm shooting for soft, low conductivity.

 

[geeks_15]

What do you plan to do? I'm also using kH and gH tests for now with my RO unit. If you get a TDS meter let us know how you like it.

Jeremy

 

[Jholden]

I plan to get an EC meter hoprfully soon. will keep you posted.