Dropper CO2 monitor

You can get any good DC here in the Sell/Trade and Power Sellers or ebays any will work
if you have a good 4dlk and bromo blue

pm mordalphus or nilocg on the forum here, there's no more powerseller section. if they can't help you out, search e-bay, pretty much all of them on there will work, but stay away from the nano ones as they are hard to fill w.o syringes and IV tubing (which is how I have to fill mine, long story) alternatively, you could make one quite easily. search DIY dropchecker and you'll find something. bromo blue is found in pH test kits or in a high school chem lab, whichever's easier. 4dhk soln can be made from baking soda, search DIY 4dhk and you'll find something.

I prefer one with white or clear suction cup.
As the clear one will turn white eventually underwater anyway.
You can use it as a white background to check the color.

I have both up aqua and glass drop checkers. I also have the 4dkh fluid. Let me know.

Thanks
Colin