Please ignore PH/KH Charts

[ricardo48]

Does anyone agree PH/KH charts are null and void especially if EI dosing or if you have a high tap GH.


My degassed aquarium water is 8.4PH and KH 12 which gives me 1.22ppm co2.

My tank PH is 7.3 which gives me about 30ppm co2 with KH 12


However according to the chart 7.3PH and KH 12 is only equal to 20ppm co2 at best.

My drop checker is 4dkh solution accurate to 0.01 and this is always yellow when my PH is 7.3

At PH 7.5 it goes green and PH 7.9 it goes blue.


Seems paying more attention to the drop checker is better than trusting the ph chart. Anyone have similar experiences?

 

[mgamer20o0]

what about your degassed tap water? the problem with the ph/kh charts is it assumes nothing is changing changing the water chemistry. often people have rocks substrate or something that changes the water and throws the readings off.

 

[jsoong]

The pH/KH/CO2 chart is only valid if there is no other buffers in your water. <The equation actually assumes pure water with only bicarbonates (from carbolic acid) in it, not even any cations ...>

Anything else in the water will throw it off, although for a lot of people, there isn't enough stuff in the water & the equation gives you ballpark figures that is good enough for our use. I generally suggest people validate the equation by making sure that your degassed tap (tank) water reads atmospheric CO2. If it is way off, you need to use some other way of measuring CO2.

 

[ricardo48]

Well my atmospheric degassed tank water is PH 8.4 and KH 12.

This gives CO2 of barely 1ppm???

My drop checker is yellow and tank PH is 7.3 so this seems about right with the 1.0 whole point drop for 30ppm co2?

 

[timwag2001]

is it possible that your ph kit isnt reading right? or that your ph kit isnt for higher ph?

 

[jsoong]

Well my atmospheric degassed tank water is PH 8.4 and KH 12.

This gives CO2 of barely 1ppm???

My drop checker is yellow and tank PH is 7.3 so this seems about right with the 1.0 whole point drop for 30ppm co2?

Since your tank water is reading ~1.5 ppm of CO2 at room air (half what it should be), you would have enough extra stuff in the water to throw the KH/pH/CO2 charts off. So go with the drop checker.

As I said before, the KH/pH/CO2 charts only give ball park figures. Don't get too hung up on the exact figure. <This is also true for the drop checker too.> The trick is to maintain a stable CO2 value. As long as the CO2 is not dangerously high (like 100), it doesn't matter much if your test reads 20 or 40. You are within the ball park of the target value. If your fish & plants appears fine, just go with it. As one of my old prof like to say: Treat the patient, not the lab test!

 

[ricardo48]

Sound advice Jsoong. I must admit my PH pen did fall into my tank one day and stopped working properly for a day. However I let it dry out and it seemed to work fine again.

Before EI dosing I use to get about 7.0 PH with good co2 ( 30ppm'ish ) and now I get 7.3 with a yellow drop checker and a lime green drop checker at about 7.5 so maybe my pen sensitivity has been damaged?

I have re measured my degassed tank water and after 2 days it now reads 8.5ph, this seems to coincide with 7.5ph of my tank giving green drop checker which is a full 1.0 point drop.


Just to be safe I am getting a new PH pen accurate to 0.01 decimal places.