noisy drain

I’ve searched for other posts but never saw resolution to the problem. With both ends submerged the only thing I can think of is that there is a leak in one of the fittings for air to enter. Here is a YouTube link to a video of it: Noisy Drain - Reefer 350 G2

Just set up 2nd hand 34 gallon cube. The water in the overflow is going into the emergency drain and making a gurgling sound. There is something that almost resembles a durso stand pipe on the main drain but not quite. I will attach some pictures and video to explain the set up a little...