KH?

[oem]

Hi Gals and Guys,

  I pretty sure I understand PH, TDS, and GH.  I also understand that KH helps moderate PH some what.  My question then is does high amounts of KH  directly affect shrimp adversely (high TDS?) or just make it harder to adjust PH for shrimp?   Or am I way off base.

    Thanks

[miniminx136]

As far as I'm aware, molecules that raise kH concentration serves as an alkaline buffer solution (mix of weak acid and strong base) and stabilizes the pH (but at a more basic pH than recommended for shrimp).

 

The molecules that elevate kH concentrations (such as bicarbonate ions) neutralize H+, causing additional water molecules to break apart into H+ and OH- to maintain equilibrium (and depending on how high the kH concentration is, they'll take up H+ again, leaving additional OH- behind), thus raising pH.

 

For example, in the equation HA ⇌ H⁺ + A⁻, HA serves as the weak acid and A- is the conjugate base (which will be a strong base). If additional strong acid is added, the H+ ions released will react with the A- to form a weak acid (Le Chatelier Principle), thus preventing a sharp drop in pH. However, when HA and A- are added in the aquarium as a buffer (for this example, in equal concentration, but the ratio is reasonably different for actual buffer solutions), the A- will have a stronger influence than the HA in determining the pH, thus resulting in a rise in pH. To calculate the pH using the concentration of the buffer solution added, Henderson-Hasselbalch equation can be used.

 

I hope this helps to some extent, and if I'm wrong someone PLEASE correct me! 

[oem]

Thanks for that explanation.  I understand the reactions of the various ionization actions as it is the same principals in my soils and substrates in my garden and hydroponics.  What I should have asked is would there be an issue with the shrimp health at higher levels of KH as it primarily helps buffer Ph?  I see most KH at 1-6 and wonder about say 30 KH?

[Mr. F]

2 hours ago, oem said:

Thanks for that explanation.  I understand the reactions of the various ionization actions as it is the same principals in my soils and substrates in my garden and hydroponics.  What I should have asked is would there be an issue with the shrimp health at higher levels of KH as it primarily helps buffer Ph?  I see most KH at 1-6 and wonder about say 30 KH?

The only issue I can see is that the pH would be driven way up as the carbonate ions could outnumber the protons in solution. WIth that being said, the concentration of acidic/bacic ions has to increase 10-fold by every point decreased/increased in pH. Bicarbonate-carbonate buffers usually have a pH of 9.2-10.8 at 1 M, which (using CaCo₃ for this) is about 40,000 ppm. Although you're not very close to the mark at all (KH 30 ~= 550 ppm), I would expect you to max out with a pH in the high 8s which is probably too high for the amount of acid produced in a normal tank. You really just want to stabilize the pH with alkalinity. If you happen to be able to get a reasonable pH with your KH 30 water, then try it out.

[oem]

Thanks guys for your answers.  I have used RO water in my new shrimp tanks with re-mineralizers but I just couldn't get that what if question out of my head.