Which type of co2 drop checker is better? Internal or external?

[Mookie]

Wondering what everyone is using and why it's better ?

[milk_vanilla]

With Internal you could reposition wherever you like/want to measure. Especially suspected dead spot/no flow

[qngwn]

I have used both internal and external.

Internal can position anywhere you want without worry about water level height.
External need to worry about water level height as it may drop below the inlet with evaporation of water.

[Urban Aquaria]

Internal drop checkers are the most commonly used, but some people prefer to maintain a clean look with less items inside the tank, so external drop checkers are the alternative. I currently use external drop checkers and found that they react to changes in Co2 levels at almost the same speed as the internal ones, so no noticeable loss in effectiveness there.

In addition, external drop checkers don't get covered in algae over time (unlike internal drop checkers), so there is one less item to clean.

[stream]

Internal runs the risk of leaking the indicator solution into the water. I wonder if it is harmful to fishes and plants. I don't think external got this risk unless you have butter fingers. :-)