Over flow gurgling.

[1fastrock]

Hey everyone.
I just set up my tank and everything is going well but my overflow seems to flow fine then slow down then gurgle and finally send a rush of water into the sump. Is there any way to fix this? I attached a video to show the problem

 

[Coral Me Impressed]

Most of the time that happens with a durso is because the flow through the drain is to fast for the size of the air intake on top. If there it doesn't allow enough air in it will create a siphon. Once the water drops enough in the over flow the siphon brakes and causes the gurgling until the water is hight enough again. I would try to turn the return pump down.