The vinyl tubing will not glue to the elbow even if it were the same size. You need to use a 1/2" barbed nipple fitting which inserts inside the vinyl tubing. How you adapt the barbed nipple to the elbow is up to you unless there is in fact something missing in the kit. The parts are common and readily available at any hardware store. Better stores like Ace and True Value may even have a 3/4" Slip x 1/2" barbed nipple in stock that would not require a bushing.
What kit did you order? It sounds like they may have mixed something up on you! From their website, if you ordered the Nano In and Out kit, it is suppose to come with 1/2" tubing and a 1/2" elbow to connect it to. If you ordered the 700gph In and Out kit, it is suppose to come with 3/4" tubing and a 3/4" elbow. However, with either option, it looks as though they haven't included the barbed nipple needed to actually connect from your tubing to the elbows! Strangely, they do include the clamps though!
Last edited by BCTate; 04-14-2014 at 01:21 PM.
Reason: spelling