jscoggs27 said:
I've read them thankyou, they are very well written and informative. That has no relevance to my question though, so I really dont see the need for such a patronising response.
Relax friend, no one is patronizing you. Many people don't read the articles and ask questions that are already answered in those very same articles. This seemed to be the case here and that's why I assumed you had not read the article. It's clear that either the articles are not well enough written or that you haven't read them well enough.
Your question has to do with electronic monitoring of pH/KH in order to determine a CO2 value. Is that right? Well I'll pull the response from the same article I referenced:
Why tank water should not be used in the drop checker
If dissolved CO2 were the only source of acidity in the tank it would be a simple matter to measure the pH and use the [KH] equation/chart to determine CO2 levels. Unfortunately this is almost never the case. There are many acid and alkaline sources in the tank varying from urine and ammonia to phosphates we ourselves add as nutrients. The pH measured in the tank is therefore unreliable because it does not accurately reflect the acid caused by CO2 dissolving in water alone.
So is this paragraph from the article relevant? Yes, it is. As Dave Spencer indicated, measurement of tank water pH/KH will not not result in increased accuracy when determining the CO2 concentration. So it doesn't matter whether you measure these parameters electronically. The pH measurement itself will be corrupt because of all the acidic sources in the tank. As a result, the calculation of CO2 concentration will be corrupt i.e. a CO2 concentration level higher than what is actually present will typically be calculated. This is part of the problem with pH controllers, because they do measure tank pH and produce a CO2 level high than what is real. This is not a problem if one is aware of the discrepancy and makes the proper adjustments, but it's necessary to understand this in order to avoid a CO2 shortfall.
Then article then goes on to explain the benefits of the dropchecker using distilled water adjusted to a known KH values in order to preserve the fidelity of the pH measurement, and in so doing, to restore the accuracy of this calculation.
I made the false assumption that having read that in the article, the answer to your question would then be evident. Does it make more sense now within the context of this clarification?
Cheers,