Does that look like a crack
Where exactly are you referring to? Maybe you can tag it with yourself so we know the area you want us to look at?
If you are referring to right below where the yellow wire enters the tube, it looks like some leftover glue. If it not then I would say it does look like a crack.
Or rather, I think what I am seeing is where the yellow wire is soldered to the end. I don’t know if I’m looking where you are talking about…
It’s right over the metal ring
@Joseph_Midjette_Sr yes that is what I’m talking about
Does it move if you rotate the box? It might be an artifact of the water/glass interface. If it rolls when you rotate the box it is likely due to the play of light where the water & glass meet. If it doesn’t move it does look like it might be a subsurface crack.
Yes it look like a crack (from other post photo), you should keep that under surveillance. more air could go in, accelerating the inevitable destructive process.
I’d say it’s not a crack, if it is the part to the right of the yellow wire over the metal find then it is a thin wire that is connecting the anode to the metal ring around the end of the tube. Mine has one of these too. If you zoom in and look closely you can see a blob of solder on it about 1/4 of the way in. Hope this helps
@David_Wakely looking on a bigger monitor, I’d agree 
Also that giant air bubble in the tube will destroy the tube you don’t get rid of it.
Now when I blow it up I see that it is the wire it had me scared there for a second
@David_Wakely I’m having a hard time getting it out
Tilt the machine
It is the wire soldered to the ring. As for the air bubble. just reverse the hoses on your pump, turn it on for a minute then put the hose back like normal and you should be good