[jmhart]

Most of us use a drop checker to measure co2. You can DIY one or order one off of ebay for about $13/shipped. You fill it with 4 dKH solution, and add a drop of methylene blue(pH indicator solution).

You suction cup it to the side of your tank. After 30 minutes, you observe the color. Blue is too low in co2, green is just right, yellow is too high. Green is meant to signify 30 ppm of co2.

 

[Darkblade48]

A drop checker used with a 4 dkH reference solution can give you a good estimate of your CO2 levels. The bromothymol blue indicator that is added with the 4 dkH reference solution turns green when your CO2 has reached 30 ppm. That is essentially all you need to "measure" CO2 in a tank.

In essence, a drop checker works on the principle of diffusion. Naturally, there will be some CO2 in your water if you are injecting it. At the air/water interface inside the drop checker, CO2 is actively diffusing from the area of higher concentration (the water) to the area of lower concentration (the air). The CO2 then proceeds to diffuse into the 4 dkH reference solution (with the bromothymol blue indicator). As this occurs, the bromothymol blue indicator begins to change colours.

As the concentration of CO2 increases, more of the bromothymol blue is changed such that the colour change becomes visible.

Edit: Ninja'ed!

Most of us use a drop checker to measure co2. You can DIY one or order one off of ebay for about $13/shipped. You fill it with 4 dKH solution, and add a drop of methylene blue(pH indicator solution).

Bromothymol blue

 

[jmhart]

Bromothymol blue

roud: Thank you, brain fart

 

[elihanover]

I don't mean to steal your thread, but I have a question, and this is as good a thread as any to ask it:

I haven't changed my drop-checker solution in over a year and a half. It still works great, so should I change the solution? Is it normal that it still works after that long?

 

[Hoppy]

I don't mean to steal your thread, but I have a question, and this is as good a thread as any to ask it:

I haven't changed my drop-checker solution in over a year and a half. It still works great, so should I change the solution? Is it normal that it still works after that long?

The pH indicator solution in the drop checker is a dye solution, and dyes are notoriously unstable, especially in strong light, like in a lighted aquarium. I think that argues that the solution needs to be changed every few weeks.

 

[C2C]

The pH indicator solution in the drop checker is a dye solution, and dyes are notoriously unstable, especially in strong light, like in a lighted aquarium. I think that argues that the solution needs to be changed every few weeks.

if you have a sump can you put it in there

 

[C2C]

and what is a long term monitor for co2 that you dont have to change every couple of weeks

 

[Darkblade48]

if you have a sump can you put it in there

While you can put a drop checker in the sump, having a sump in a planted tank is contraindicated because the sump will off gas a lot of CO2.

and what is a long term monitor for co2 that you dont have to change every couple of weeks

There are electronic CO2 monitors/probes that are made, but are quite expensive. You may likely want to use a drop checker to save money.

 

[elihanover]

While you can put a drop checker in the sump, having a sump in a planted tank is contraindicated because the sump will off gas a lot of CO2.

That's not always the case. As long as it's sealed/covered properly, the problem can be minimized.

 

[C2C]

so how do you put a drop checker in the tank without spilling

 

[elihanover]

so how do you put a drop checker in the tank without spilling

Very carefully. If you spill some, it's not that big of a deal.

 

[C2C]

???

 

[elihanover]

Just hold it upright, and stick it to the side of the tank. The solution won't hurt your tank, and the dye is so small an amount that it won't affect anything if it spills.

 

[C2C]

how do you put the dye in and turn it up right without spilling it
so if i accidentally spill all of it in my tank nothing will happen

 

[elihanover]

Put a small amount of the 4dkh solution in a plastic cup, put a couple of drops (enough to show a distinct color) of the PH indicator solution in the cup, mix them, then using a pipette, put the mixture into the drop checker while tilting it toward the ball part. Then turn it over, and put it in the tank.