How To Use This Eheim Co2 Regulator?

[dingweding]

This is a second hand CO2 regulator I got years ago, I used it on my tank 2 years ago, it only has a single meter, adjust by the needle valve.

However stupid me forgot how to connect it, I got it out today want to use on my new tank, but I notice it does not fit normal air line, as you can see from the second pic, the normal airline is too big for it. the out port of regulator seems only about 2mm

any suggestions? many thanks

 

[dingweding]

ok, guys, I found a way to connect it, but I have new problem now. It seems there is a huge leak at the connection between the regulator and co2 bottle.

My other regulator need tool to fix on the co2 bottle, but this one, as shown by the left side of first picture.

I only need to turn it and screw it on the co2 bottle by hand, however there is huge leak. I do not what kind of tool can help me to tight it, anyone can help? thanks