Same here. The dudes instructions say you don't need i. I have no idea how he makes it work without it. Luckily I had some 3/8 ID silicone tubing sitting around to use. Which works fine.I've also noticed that the tube that is used to cover the filter in order to make it stick in the hole of the stainless steel float is too small. There was no way for me to cram it on there. I would order a mm or 2 larger.
A note for those making this build you only need like 1 inch of 3/8 tubing per floating dip tube. Most LHBS carry it by the foor for maybe $2-3 per foot.