Alright here's what i got. I bought an Eheim co2 injection kit a couple days ago. It came with a diffuser, tubing, needle valve,pressure guage, everything i should need for pressurized co2 except for a co2 tank. Ok....so I bought a filled co2 tank online and finally got it yesterday. I went to hook everything up and noticed the pressure guage won't fit on the co2 tank right. The pressure guage threaded area has a large allen fitting inside it. When I go to thread on the pressure guage the large allen thing won't fit inside the threaded area on the tank properly. It's obvious there is something wrong. Is there always a problem getting these Eheim pressure guages to fit onto co2 tanks, is there some kind of adapter? Here are some pictures so you can see what I am talking about.





