Oyster shells

[axolo]

Hi,

Do you guys use oyster shells in your pond avoid having no more KH in the pond ? (I have very soft source water here)

The GH get's a boost too by using it.

CaCO3 + H20 -> Ca++ HCO3- OH-

p.s. yes i know I know NaHCO3 dissolves better

[Duncan]

hi

thanks for the chemistry lesson
Oyster shell is a pretty poor buffer yes there is carbonate to be had, but its locked by the calcium
Its not released at all till the water goes acidic and even then its a very , very , very slow process. you would have a crash long before

dunc

[Manky Sanke]

I very much agree with that. I have, for many years on various forums, warned that oyster shells, cockle shells and snail shells are poor buffers. I often ask this question to underline that point; if, at normal pH values, oyster shells dissolve as readily as those who are selling them would have us believe why aren't oysters in natural environments all naked?

[DaveB]

I very much agree with that. I have, for many years on various forums, warned that oyster shells, cockle shells and snail shells are poor buffers. I often ask this question to underline that point; if, at normal pH values, oyster shells dissolve as readily as those who are selling them would have us believe why aren't oysters in natural environments all naked?

Wish I had taken the above advice before spending £200 or more. It did raise the K.H. value as I used loads of it but as both Duncan & Syd say, it did not prevent the p.H from swinging as it did not react quick enough.After removing it from my system the colours on the Koi improved as well.Save your self a load of money and use bicarb. Best Regards Dave

[axolo]

Ok, but if i use NaHCO3 for the KH and CaCL2 for the GH, i am actually adding salt to my pond, and I have some plants who cope very bad with even small salinity.

I calculated -> going to KH 10 & GH 10 (from KH 3 and GH 2) is like adding 200g salt / m^3.

[Manky Sanke]

I’m not sure why you would want to increase the GH from 2 to 10. Lower values of GH tend to favour good colour development, especially beni (red). Many koi keepers actively try to reduce their GH value by using RO in order to emulate the low GH and KH values in Japanese mud ponds which are fed by mountain stream with very low mineral content.

If you did want to raise your GH why would you want to add calcium chloride (CaCl2)? Why not use calcium carbonate (CaCO3) as you originally suggested? Calcium carbonate is easily added by oyster shells, cockle shells, eggshells, limestone chips or proprietary products such as Lithaqua.

Also, raising a low KH value from 3 to 5 is fairly common but raising it to 10 seems excessive.

[Duncan]

hi there

stick to 5's a gh and kh of 5 is about where every one should aim to be that's what I class as ideal, that would put your pH somewhere in the mid 7's which again is ideal

dunc