Ah, I haven't used a LifeReef in a billion years. You can definitely use vinyl tubing on that with the clamps. No need for PVC. Maybe a T fitting to merge them into to to go into the single intake on your sump.
ETA - However, I wouldn't do that T fitting. You want backup standpipe/overflow tube in case something gets clogged. Ideally, you want the two pipes from your overflow going into the sump separately. That said, my through the glass overflow has two standpipes and I just plugged one of them off. Knock on wood, I haven't had issues