[rich815]

Drop checker.

Here's ya' go:

http://www.greenleafaquariums.com/co2-drop-checkers.html

(be careful of the ones that are cheaper and tell you to use tank water in the checker, they are not accurate).

And here's a fantastic thread about them and their use (accurately!):

http://www.barrreport.com/articles/2661-drop-checkers-co2-indicators-why-how.html

 

[rich815]

article is a great read, but i wonder which drop checker is better. the double chamber or single chamber

They are both better.

 

[rich815]

better than nothing, of course, but out of the 2. which one is preferable over the other.

I have both in my main tank. They both work fine when used properly.

 

[rich815]

I'm betting that it won't change back once the "chemical" reaction has taken place, and that you (we) would have to periodically put new solution / reagent in the checker.

No, and yes. I have two drop checkers. One is a plastic one from Red Sea (unfortunately one whose instructions tell you wrongly to use tank water) and another the double bulb Cal Aqua one which comes with two fluids (one the "right" colored one that the other you watch to get it to match).

The Red Sea one I use with 4dKH water I made myself and it works great. My CO2 goes on 2 hours before my lights do. When the lights first go on the DC is a medium green slightly edging towards blue. Within an hour and until the lights go off 8 hours later it's a nice lime-green, maybe leaning to slightly yellow. My CO2 goes off one hour before my lights do. I replace the 4dKH water and add 2 new drops of reagent in the Red Sea DC every week after my 50% water change (I pretty much follow a basic EI fert and dosing regime) as I have found a protein film occasionally forms over the hole and sometimes after a week or two it seems to not change color anymore.

The glass Cal Aqua one also works great. I have not changed either fliuds in this one since I got it almost 2 months ago. The color of the test bulb changes color throughout the day/night pretty much along with the way my Red Sea one does as described above: blue/green in the early morning before the lights go on, green leaning slightly towards blue once the lights do go on (again, CO2 went on 2 hours before this), and within an hour of lights on matches the "matching" color bulb until again the lights go off after 8 hours.

Why do I have both? Well, someone was selling a two-times-used Cal Aqua one for cheap with fluids and I grabbed it. I now use them both in my 72 gal, located in different parts of the aquarium, just to feel good about my CO2 being close to correct in different areas.

 

[rich815]

ok, so your color does change...can someone that has a single bulb DC chime in on how their color changes, if at all?

Guess I should have been more clear. The Red Sea one is a single bulb. I have both a single bulb one and a double bulb one. They work on the same concept.

 

[rich815]

The way the DC works is by gaseous diffusion. CO2 will diffuse from a place of high concentration (your tank) to a place of low concentration (the checker). This will continue until the concentrations are equal. If the concentration of CO2 in your tank decreases the process will reverse. This is a fairly slow process so it takes a relatively long time for the DC and tank to equilibrate.
At night your tank will lose some CO2 but it doesn't drop that fast so you don't see much of a change in color. (The color change is not that accurate of a measure of the CO2 concentration). You can "check" your checker by taking it out of the tank. It will turn blue rather quickly.
I use one of those "cheap" Red Sea checkers and it works fine. The only thing you have to do that is different from the directions is to use 4 deg. kH water instead of tank water in the bulb.

Exactly, well put.

I should add that the Red Sea checker having in essence a white background for the checker liquid, is a lot easier to see the color than the pretty and more elegant looking glass Cal Aqua checker (double or single bulb). I sometimes use an old white plastic credit card I keep in my under-tank cabinet and put it behind the Cal Aqua glass bulbs to be able to read the colors definitively. The Cal Aqua bulbs being all glass and clear, and having plants, wood and fish in the background makes it harder to see the liquid color sometimes.

The Red Sea checker (this photo shows it empty, but you can see that with liquid it does have a white background to help see the liquid color):

 

[rich815]

Anyway, reading what you folk say about the use of a credit card, gave me a little idea.

I just got mine from Aquaticmagic and it comes with a PH colour strip. My thought was to glue the colour to a piece of white cardboard and get it laminated...

Is this so you can match the color to the strip? It's really not needed. Lime-green is lime-green and is pretty easy to see. It's either blue, or a definitie blue-green, which means too little CO2, or a strong yellow, which is too much. My use of the white credit card was just because the completely clear bulb is too hard to see what color is in there. The white card gives the temp background to see the color.