Drop checkers in use for CO2 monitoring around here?

If not, they look like a good thing... I'm going to make one very soon.

Good thread (follow the out links) detailing principles, sources, DIY, how to make KH standard solutions etc. etc. etc. over at AA - also see looking for those CO2 measuring bulbs

I hope nobody here considers it poor form to mention them, but 1) they are another good source of information; 2)I searched all over here and found nothing on these devices; 3) and they have already returned the favor by calling out the article on fishless cycling found here.

My proposed design:
glass tube bent into a "M" shape, 4 or 5 KH solution & indicator into center section, 1 suction cups, stick it to side of tank.

If the materials are cheap enough, I may have to go into business selling these w/ dropper bottles of indicator premixed w/ 3, 4, 5 KH solutions...

Hutchewon said:

Do you mean bubble counters? CO2 is a gas unless highly compressed. Kinda hard to measure as drops.

Click to expand...

Nope. A "drop checker" uses a pH indicator in a standardized solution so that CO2 concentration changes the pH, hence the color, of the solution. The air in the checker reaches equilibrium with the gasses dissolved in the tank's water. The CO2 then reaches equilibrium with the solution in the checker. If there's enough CO2 to drop the pH the right amount, the solution turns green. Too much CO2, it turns yellow, too little=blue.

Red Sea's version uses a gas permeable membrane so there is no need for the air gap between the tank water and the indicator solution - theoretically, this will result in a shorter lag time in getting a good reading. I may be able to do this in a series of small vials that would indicate CO2 over a fairly wide range(drum roll) simultaneously. I have to see if I have the right kind of membrane... the vials, caps, suction cups are all done.

kjf91004 said:

APC has been talking about these for a few months now. It seems that to get the best results, make up your indicator solution with a Kh of 4 degrees. That is where you get the most color change with changes in CO2 levels. You don't need or want the Kh to be the same as your tank.

Here's the link at apc. It includes examples of DIYs.

http://www.aquaticplantcentral.com/...-diy-drop-checker.html?highlight=drop+checker

Click to expand...

Thanks for adding that link, I had misplaced it! - it is the location of most of the DIY ideas.

4dKH is a good default starting point, but for some situations, I could see people wanting their checker to go green at different pH/CO2 combinations (4dKH will go green only in certain combinations of pH/CO2 levels - ppl w/ pH that's off or who want more/less CO2 may want different dKH values so they can see green now and then as well). From the above referenced thread, see pg 14 of the thread for the pH/CO2 relationship...

sano drop checker in action


There's a hole in the yellow cap, a gas-permeable membrane covering the opening of a 2mL sample vial. All held in place w/ a suction cup for mounting xmas lights (small ones) in windows.

It's cheap & doesn't leak.

test solution is 4dKH pure water, API pH test solution.