plumbing question

My duruso's are almost level with the tank water height, I do get a kind of surging (belching) noise where the water enters the sump, I have air holes drilled in both my duruso's but no adjusters for the air.

 

Ok, I debated whether to put this out there BUT to let you know how nice our friend (that built my sump) is. I asked him to look at what a durso was and gave him the website to check out. He texted (is this a word?) me back and said "don't buy this, call me." Well, it turns out I already have a durso DOH - it's black and my tank back is black and the way it was positioned, I couldn't see the hook portion. He was so nice about it, and just gently said you have one of those on your tank already - not well, I knew you were clueless but etc. He is going to add in a pipe (he said the drain pipe is actually shorter than it should be) so that we can raise the durso up higher which should bring the overflow water height up. He's almost done with my hood which should also help with the noise.

Thank you to all for responding!