What are these?

[Fishkeeper26]

I was watching videos on YouTube about planted aquariums and saw these things a few times.
In the first picture what's the little tube? (In the upper left) and in the second what's in the lower left hand corner that has really fine bubbles coming out of it?

 

[fort384]

Drop checker (for measuring CO2 levels) and CO2 diffuser.

 

[mfdrookie516]

the one on the top left of that first picture is a drop checker... the bottom right on both is a glass diffuser

 

[TropicalAquariumExpert]

Drop checker looks distracting in this small tank, and diffuser could be hidden behind the rocks and grass as well.

 

[Fishkeeper26]

Thanks how does the dropper measure CO2?

 

[fort384]

It uses a pH indicating solution that changes color based on pH. CO2 injection lowers pH.

 

[Fishkeeper26]

Oh ok, thanks!