Top thread Al. Thanks for sharing.
I've put up a link to this in the pinned CO2 thread.
B) Cheers George.
Hopefully others will give this a try and give some feedback. It only takes about 30mins to set everything up.
For anybody wanting to try this, here is a quick summary on how to set it up ...
Requirements:
Drop Checker. (I use a glass one, but plastic or DIY one will do perfectly well)
Distilled Water.
Bicarbonate of soda (not baking powder!)
KH test kit. (I used the Nutrafin KH test kit)
PH test kit. (I tried both Nutrafin and Tetra test kits)
Mixing the reference solution:
I did a KH test on the distilled water, 1 drop (nutrafin) turned it yellow, you need to aim for a dKH of 4 by adding small amounts of bicarb of soda.
Just mixed a larger batch of solution up and 0.1g of bicarb of soda was enough to raise 1ltr of distilled water to approx 4dKH. So you see we are talking VERY small ammounts.
The tiny measuring spoon from a Tetra NO3 test kit, each one gave approx a +2dKH rise in the 100ml of distilled water. So 2 of these spoons got me to roughly 4dKH.
Fine tune the reference solution:
One you're around 4dKH, it seems best to 'fine tune' the solution to give a greater accuracy with the CO2 measurement. With the Nutrafin KH test kit uses 1 drop of reagent equals 1dKH when testing with 5ml of water. I used 20ml of distilled water (As advised by VaughnH) so that each drop of reagent equals .25 dKH, this allows to fine tune the solution to the required level. I found it's far easier to add a few drops of water and bring the KH down that mess with the tiny amounts of bicarb needed !
I now have a reference solution that turns yellow at 4dKH +/- .25dKH accruacy !
Fill the drop checker:
Once you are happy with your solution you simply add it to the drop checker. The easiest way to do this seems to be with a dropper. I used the ones that came with some Seachem Flourish. Fill your drop checker bulb approx 2/3 full
Any spare solution can be stored for refilling the drop checker. I'm not sure how long the drop checker solution lasts for, but I believe it's a few weeks.
The final stage is to add a few drops of PH reagent. You need to add enough to give a distinct colour to the solution, without making it too dark/opaque.
At this stage your solution should be blue, showing that you have very little Co2 in the solution.
Place the filled drop checker into the tank about 3 inches below the surface.
This method takes a bit of time for the reference solution CO2 to equalise with that of the tank. After 2 or 3 hours your drop checker should have changed colour.
Green means you're pretty close to 30ppm.
Any hint of blue shows low CO2, any hint of yellow shows your CO2 is high.
NOTE:
Personally I like this method as an easy visual reference that nothing has changed.
I wouldn't use it totally 'stand alone' but use it in conjuction with other observations, particularly those of your fish ... if your test shows green, but the fish are at the surface gulping .... something is wrong !
I think there is probably a margin of error in just about any test method, especially where we judge readings against a colour reference.
I do however think this method is closer than most, as you have an accurate KH solution and the readings cannot be affected by anything else in the tank that may influence PH/KH !
Cheers
Al
