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[APD] Using a reference KH with a pH probe meter

Scott et al, 

The good idea from all this is the fact it gets around the KH
issue in the tank and variation it can cause.

We have folks claiming 50-200 ppm ranges of CO2 based on the
pH/KH test readings and the fish are just fine, others have
35-50ppm and dead fish...........we know there's screwy issues
with our assumptions about KH.

By using a referenced solution for the KH, we eliminate one
variable/assumpotion that has been causing issues for sometime,
but by using a pH color change to measure, we lose some of the


So this **obviously** leads us to make a referenced KH solution,
that we can __insert a pH probe into__ so we can get very
accurate deterimination of CO2 ppms.


That way we have successfully removed the KH interference issues
from the tank water and still have saved the accuracy of the pH

You simply add the pH meter inside the solution of the drop

Now that is **my idea** and one that would work very very well
indeed. **Of course Gomer and Vaughn** also get credit for Ref
KH solution (haha), but I've always just used the tank itself
and done a huge water change with RO water or known tap to set
the CO2.

Much like making a ref solution when you use EI and getting out
of testing the water for NO3 etc.

Which is a similar thing...........but this way anyone without
RO or having an unknown KH influence/interferences could get
around this and both the pH and the Kh are referenced, unlike
the old method of merely assuming the KH is all bicarbonate.

A similar set up is used but uses an IR for Limnology for the
gas rather than a reagent based liquid etc.

So a small vial with the ref KH solution is added with an air
gap to keep it seperate from the tank water, the solution has a
pH probe with a rubber gasket inserted into it, that reading is
referenced to the pH/KH table.

Basically you make a large probe holder with an air gap and a KH
ref solution inside.

That should be cheap and solve both issues.

If you don't wanna fork out the $ for a meter and are fine with
color metric test for pH, then this is a great idea also.

Either way, you come out ahead and have a mucher higher
confidence and accuracy in your assumptions for the CO2 ppms at
any point during the day being that both are continuous

That will be cool for many who are frustrated with measuring

Now with that extra acrylic I sitting and the viewtainers, and
those nice rubber grommets, I can make a nice little KH ref
chamber for the pH probe:-)

Then you can measure CO2 in tannins laden water, ADA soil, funky
tap, most anything.

Greg will not sell such solutions, liquids are harder to ship.
Someone would be wise to offer a series of KH ref solutions in
500ml amounts to 1ppm or less resolution using a 0.001 gram of
lower scale using DI water.
Say 0-1-2-3-4-5-10-20 degree ranges.

So there you have it, another excellent way to measure CO2 very
accurately and gets around intereferences from the tank's water.

Gievn the importantce of CO2 measure in our tanks and it's
relation to algae and plant growth, I think folks should be very
critical about CO2, I nag folks a lot about this:-)

But......even this pH meter and ref solution will not address
the intereference a CO2 microbubble might have.

Unlike the O2, Ar, N2 gases, these are non acidic and a will not
affect the pH readings, one could make a deterimination as to
the relative % change based on the CO2 mist method floating
around the water vs and standard reference.
No other gases will affect the color or the pH in the ref

This, in a sense, would allow you measure the true plant CO2
availability of the mist/dissolved fractions together.

The other more obvious way is to measure the differences in O2

I've already done that and found roughly 20-40% increase in O2
production using a calibrated YSI DO meter.

Still, it's interesting to try out another method to measure CO2
with/without to see if the affect is close to the % increase in
plant production.

I just had this idea drawn out and had my lawyer notorize it,
now I'll have him apply for a patent pending.
Don't worry Gomer and Vaughn, you get 1/3 ea:)

Tom Barr



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