This is a discussion on ok so here it goes... within the DIY Aquarium forums, part of the TFK Resources category; -->
i bought the jungle CO2 system for my ecplise 5 corner and it doesnt fit...well the long plastic part anyways...any ideas on how to ...
After looking at the picture of the unit, the only way I can see to modify it to fit would be to cut a section out of it until it's small enough, then use either waterproof plastic cement or 2 part epoxy (powerpoxy brand) to reassemble the end to the main piece.
You might want to consider an easier way... send it back and tell them it won't fit into your tank, and then instead of their unit, go to the LFS and find a limewood air block/diffuser and use that instead. The wood has smaller pores than something like an air stone, so the bubbles come out small enough to avoid wasting CO2 while still getting your desired effect. The limewood blocks are often sold for use in protein skimmers, and shouldn't cost more than what you paid for that unit in the picture.