Be careful. If the bottle keeps on collapsing like that, you will end up with the yeast mixture inside your aquarium! It is possible the Hagen Elite Mini is too strong, causing the pop bottle to collapse like that.
Happens to me all the time with my bubble counter. Usually it is when the filter intake is clogged with plant debris and other stuff. It makes the pump suck a lot harder on your air tube rather than sucking tank water. See if this is the case.
I was following that one thread at that one other forum, but yea I checked it and it didn't look like their was gunk, but I cleaned it a little anyways. I do have a stockign rubberband to cover the slits because I have babies in that tank.
pinch off the hose let some pressure build in the bottle for a min or two it should do the exact opposite of implode unless you have suction of some sort on the other end
I just took off the stocking that I rubberbanded onto the filter. Hopefully I won't see any chopped up baby guppies all over the place. Well I guess they'd get stuck to the sponge covering the output thingy.
To the OP I dont know but I would be cautious and start planning an upgrade. I had a home made set up and I just stuffed the connection between tank and bottle - I couldnt get a seal. So I cracked it and spent money on a set up bottle (Dupla brand) and just have this starting. A much more solid bottle. See I can make and hang a door on the stable but am useless with little bottles and silicone (note am not a boy either) .