[GSAS-Member] Who's using a drop checker in their planted tank?

[Matt Staroscik <matt@wrongcrowd.com>]

I just installed mine but I think it is not working properly and I wanted
another opinion. Obviously they are very simple and there is not much to go
wrong, but I think my 4 dKH standard solution is bad. I have the Red Sea
model, by the way, which comes with indicator, but no standard solution.
They tell you to use tank water, which I don't want to do as the tank is 6
dKH and has an unknown amount of phosphates etc in it.

I made the 4 dKH standard myself with baking soda, RO/DI water and a series
of dilutions. A KH test kit verified that it is correct, but as I used
kitchen glassware maybe there was enough residue from detergent to mess
things up. My RO/DO filter shows 0-1 ppm TDS as it should, so it is still
working well... but maybe not well enough for this.

When I added the indicator to the solution, it immediately turned green,
about the shade of green that you want to see when the CO2 in the aquariumis
at the right level. For a sample of the reference that has not had CO2 added
to it, the solution should be blue, right?

In the tank, the solution in the drop checker stubbornly stays green, even
after the overnight lights-out.

I put a sample of the solution + indicator into a graduated cylinder to see
if it was sensitive to pH changes at all. If I blow in to it with a straw,
the CO2 in my breath turns in yellow, as expected. Shaking it to drive off
CO2 got it down to blue. The strange thing is, it stayed blue overnight. If
the solution was off I would have expected it to bounce back to green when
left alone.

Some forum posts have said that drop checkers may not work right until they
have broken in for a week or so, but that just doesn't sound right to me.

Does anyone have ideas, and/or a convenient source of good 4 dKH reference
solution? It's easy to make, but maybe not easy enough to make one that's
pure enough in a kitchen.

Thanks,
MS
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