Testing low kH ?

[onlyme]

Would someone be good enough to tell me what they use to test soft water perameters with please? Are there specialised reagents or are electronic meters used?

Also when testing low gH with a conductivity meter is there a way to differentiate the various ions in solution?

Soft acid water is a whole different world to keeping Malawis!!!!

Thanks,

Craig.

[Brett4Perth]

Hi Craig,

My understanding is that all the electronic meters commonly used measure conductivity, even though they may give a read-out in degrees of hardness/ppm. They just use an algorhythm to convert the measurement.

Conductivity depends on the concentration of ions in the water, it is not specific.

I tend to use test kits to measure general(Ca and Mg) and carbonate (bicarbonate) hardness. Not exactly sure about the chemistry of these kits and I doubt they are very accurate. More of a guide.

Are you trying to achieve water of low hardness, conductivity or total dissolved solids?

Cheers

Brett

[onlyme]

THanks Brett!

I am trying to achieve soft acid water. I believe some carbonate ions are neccessary for the biological process to occur in any water and as I am using rain water I reckon I need to add something? As you say reagents are only a guide and at these low levels too inaccurate to be of any use. To digress, I have found reagent tablets to be much more accurate and not as subject to shelf life as are liquid product. My understanding of conductivity meters are as you have stated and only assess the free ions conducting current. The use of bi sodium phosphate alone to lower pH would render a measurement of gH tested by conductivity wrong.

Maybe I am missing the point here somewhere because I seem to be chasing information that no one else uses?

Again thanks,

Craig.

[DarwinBlueEye]

Hi Craig,

Don't know how scientific you want to go on this one, but as someone who's been keeping South-American dwarfs in planted tanks for a while, I can give you the following opinion:

I'm a bit of a fiddler, so early on I was was quite concerned with keeping water parameters just right. I did use Dupla test kits (with which you can measure to as low as 0.5dKH, whatever that is in ppm).

Having said that, I soon realised that I was wasting a lot of money on test kits, since my tap water was very soft (<2dGH, 1dKH, pH7.0) and wasn't changing a lot. So my main concern these days is to have a sufficiently high KH to buffer the tank pH (which I try to keep around 6.0-6.2 with CO2). With a low KH (<4dKH) you'd get serious pH swings otherwise.

I'm keeping the KH up using the following formula:

1/4 tsp of sodium bicarbonate (baking soda) per 50l of water will raise the KH one degree. 1/2 tsp. of calcium carbonate per 50l of water will raise the KH and GH by one degree (but I tend to keep the GH I'm blessed with ).

So if you're gonna use rainwater you shouldn't have any dramas, since you'll be starting out with know KH and GH (zero for all practical purposes).

Of course if you have hard tap water and want to bring GH and KH down then that's an altogether different saga

Cheers

DBE

[Brett4Perth]

Hi Craig,

Soft, acid water I presume is to keep your dwarfs happy and ?breeding.

Not all dwarfs require the same water conditions and some are much more tolerant than others. Given this, most still do better in soft acid water, which as mentioned above is inherantly unstable with respect to pH.

I have looked around on this topic for quite a while and there seems to be precious little info on which is the most critical factor. Generalisations like "soft,acid" abound.

Most of the parameters we measure are just guides to the concentrations of the various molecules/ions in the water. As you know, water of low hardness is generally of low conductivity and low total dissolved solids. But which is most important. I really don't know.

Traditionally peat softened water has been used with success. Do the tannins have some beneficial effect or just bind up the ions ( Ca and Mg mostly). Is osmotic pressure the key, theoretically I can see how this could be important.

From what I have read, it seems that conductivity is more relavent than hardness.

When I have access to safe rain water I think the easiest option is just to dilute your tap water. So I might do a tank with 50:50 or if I want it very soft 75:25 rain:tap. I don't tend to bother trying to measure hardness at these levels as my water is pretty soft to start with and I know the tests won't be accurate.

Perhaps if I had a conductivity meter??

Cheers

Brett

[onlyme]

You are right Brett, there is precious little to access in the way of good information regarding the chemistry of soft, acid water. THis is why I also have question as to whether it really matters. Maybe near enough is good enough. My fish room is now self sufficient on rain water in a 10k litre plastic tank. The few Eucalypt leaves that get in it from the shed gutters are enough to further reduce the pH. It is now running at 6.7~6.8 as opposed to 6.9 which it tested when new and clean. It appears that peat both chelates and lowers pH, I assume the high tannin content of peat forming tannic acid is what lowers the pH. I have a 225 litre tank I am going to test clean and then run a filter with peat in it and test again and see what I get. I dont want to use bi sodium phosphate to lower pH because I nether want the fertilising properties of the phosphate nor the sodium ions in the water. THis tank will go to discus as soon as I feel it is safe. I too have a conductivity metre on the list of "to buys".

Cheers,

Craig.