pH & Hardness chemistry

Hi all
I would like to set up a Guppy & Corydora tank.
My water is treated borehole water with pH=7.9 and dGH=0.75 (13.4 mg/L)
With the hardness being so low, I want to raise it to at least dGH=8, for the Guppies to thrive. How do I do this without affecting the already high pH?
I read somewhere that carbonate (shells and coral) will increase pH in water until it reaches about 7, at which stage it has very little further effect on pH. Is this true? Is crushed shells/coral the way to go? What would the "dosage" of such treatment be?
Thanks for your time!

 

There are numerous products out there that'll do the job, but I use Seachem alkaline buffer to raise my KH and Seachem Equilibrium to bring up the GH.
Used them for years and can recommend.

 

Thank mate

 

Hi @Xerxes You can use crushed coral that will naturally buffer the water gradually. It is fairly inexpensive and continuously dissolves into solution as your alkalinity drops. I use crushed coral in all my tanks and my pH stabilizes just below 8. The solubility of CaCO3 (essentially what crushed coral comprises of) drops off steeply beyond a pH of 8:



So you dont have to worry about it continually dissolving increasing your pH beyond control. Also, because it is an equilibrium between the coral and solution you can not overdose. Just put some of it into a stocking and put it into your biofilter or hidden in your tank somewhere.

 

Hi Zuraki - thanks for your advice - one question, where in Cape Town do you buy your crushed coral? I've been looking online and can't seem to find it anywhere local, all I see is the fine crushed coral "sand" substrate.