That picture looks like the "mods" I described in that other thread...
The lowering or "shortening" of the lower tube and the addition of an airstone...
In researching these mods I read that the inner tube is not glued, just a press fit, and should come out with a bit of persuasion...
I was not able to remove mine either, but I am pretty "handy" with a Dremel tool so I just cut it out with a mandrel and cut off wheel...
Perhaps you could "borrow" one from a friend or better yet, buy one... They are not that expencive and will come in handy for so many DIY projects around the house and tank, that it'll pay for itself rather quickly...:yes: