[Mcnugget]

can someone help me with this summation? i am guessing that since 24+5 dne 80, there is some other element that is the other 51ppm? this seems like a large number that should be accounted for. is there a list of usual suspects or am i interpreting this incorrectly?

I think where i'm going with this is i'm about to mix up my first PPS macro bottle from GLA, and between my tap TDS of 275, and these numbers, i was debating cutting the Mg portion in half...

thanks,
cory

 

[Mark Fisher]

The units are different. Ca and Mg are expressed as ppm (parts per million), while hardness is expressed as gpg, which I assume is grains per gallon of CaCO3. 1 gpg = 17.12 ppm.

 

[Mcnugget]

The units are different. Ca and Mg are expressed as ppm (parts per million), while hardness is expressed as gpg, which I assume is grains per gallon of CaCO3. 1 gpg = 17.12 ppm.

The hardness is listed twice I think, once in ppm and once in gpg (the 17.12 relation is correct to go between the 2 numbers). Using all of the ppm entries, they didnt seem to add up to me. Am I still reading wrong?

 

[Mark Fisher]

The hardness is listed twice I think, once in ppm and once in gpg (the 17.12 relation is correct to go between the 2 numbers). Using all of the ppm entries, they didnt seem to add up to me. Am I still reading wrong?

Wow, I did not see the other ppm value. Do I need glasses?

Anyway, hardness is expressed in ppm CaCO3, while the Ca and Mg are expressed in ppm as cations. The atomic weight of CaCO3 is 100.08, while Ca is 40.08 and Mg is 24.31. So, multiply the Ca value by 2.497 and the Mg value by 4.11 to get the equivalent CaCO3, which is 24 * 2.497 + 5 * 4.11 = 80.47

 

[Mcnugget]

Thanks for that. HS chemistry suddenly flashing back... I take it its just always assumed that those two are the only significant mass in hardness then.

Since I seem to have a good source (of help and Mg), do you have any opinion on adding the full amount of Mg to the PPS MIX? I understand the extra won't harm anything, but may help keep my TDS in line if I start to use the meter as Edward suggested on his page if the extra Mg isn't needed....

 

[Mark Fisher]

Yes, you have enough Mg in your water, as long as you do regular water changes. I wouldn’t add the full amount of Mg to the PPS mix unless a deficiency reveals itself.

 

[Mcnugget]

Thanks for helping me get started. This tank was my daughters Xmas present that she immediately tired of, and I was happy to take over. I think its been 20 years since my last tank and so much has changed.