A question for Biotypical..

[lesley]

Hi Biotypical,

I have been reading the thread "re kH to low". This helped me gain valuable info on this subject.

a question please... I am still coming to grips with this, so my question may not be phrased correctly, you may have to read between the lines and use ESP!!!!

I have been having major pH crashes. kH out of tap (rainwater) varies from nil to 35 ppm (at the moment with rain, normally nil).

I am currently using calcium carbonate. This of course raises pH. If I then use a pH adjuster will I not merely be breaking the bond between the acids and the carbonate and then be back to square one?

[ChloroPhil]

I'm not exactly sure on the chemistry of pH adjusters, but the definition of making something acidic is adding a Hydrogen proton to the mix. :)

For our purposes, no, adding an acid buffer to water with artificially buffered KH _shouldn't_ affect KH too much.

If you don't mind me asking, why are you adding an acidifier? With a KH that low your pH should be just fine. There really isn't any benefit of chemically altering your pH with a buffer. It's much safer to get your fish used to your particular tap water's qualities and use that. It's too easy to make a dosing mistake and throw your whole tank into a panic with chemical buffers.

Why does increasing the KH of your water increase the pH? Because your water is now more able to absorb those errant H protons given off by the breakdown of CO2 in solution, Carbonic Acid. In effect, you're chemcially negating the Carbonic Acid in the water with KH buffers. This is a good thing if you're artifically increasing the CO2 in solution. If you're not, it's not such a good thing.

By the way, using Calcium Carbonate will also increase your Total Hardness, not just your Carbonate Hardness. Baking Soda (Sodium Bicarbonate) will buffer KH only.

Hope this answered your question,
Phil

[lesley]

Hi Phil,

Well,

I have tried bicarb and found two drawbacks, I seem to have trouble adding the correct amount to not shoot the pH up dramatically and also I find that the effect is too short lived, and once it is used up I head for a pH crash. The calcium carbonate appears to be more stable. But it is giving me then a pH of over 7.5.

I would love to be able to leave my water as is, but it appears to be just too unstable. For instance if I add liquid plant fertiliser with my unbuffered water, I usually get a pH crash. If I want to go away overnight, with the unbuffered water, I am unable to leave it. So, I have to have more stable water and I was hoping to achieve a near to neutral pH if at all possible. The strange part for me is that I have been operating with rainwater since I started keeping discus some nine months ago. I started during and near the end of a six year drought. The water in the concrete tank had been there for a while and very little new water was added. It was steady at 6.8 pH and 35 ppm kH. Since the drought broke and I am getting continual additions of rainwater, my problems started.

Thanks, Lesley

[ChloroPhil]

Lesley,

That's your problem right there, rainwater! That stuff's too unpredictable, if you can use city water. If you don't have that, try putting a few small pieces of coral skeleton or clam/oyster shells in your filter, they'll be a little more stable.

Don't forget your CO2 either. If your KH is reducing a few days after adding it, the best bet is that your plants aren't getting enough Carbon from CO2 and are breaking down the Carbonate to get it, which will screw with your pH. My best suggestion is to add CO2 gas then use Baking Soda to get your KH up to where you want it.

Barring that, shells in your filter will be better than chemical dosing.

Best,
Phil

[lesley]

thanks Phil

[Paulio]

This page has a wealth of info on the pH-kh relationship as well as great info on all nutrients and effects.

http://www.csd.net/~cgadd/aqua/

Paul

[lesley]

thanks Paulio

[ChloroPhil]

You're welcome Lesley. Keep us updated with your situation.