Down Pipe Noise!!!!!

[JMassens2002]

So I’ve been trying to make my down pipe shut up and nothing seems to work if anyone can help please it would be very much appreciated. I’ll attach a video but basically the issue is that drains and fills and drains and fills. So there’s really no constant flow and it make a huge gargling sound in my sump/reef matt, idk if that makes a difference, but yeah please anyone.
Side question my tank is a mixed reef what’s considered the perfect level for nitrates? I’m testing with a Hanna tester and it came back as 4.0 so just wanna check with everyone?

 

[Jason_MrFrags]

Do you have just the 1 drain? What is the other pipe? Its getting a full siphon and then drains down til it sucks air and breaks siphon. You can drill a small hole in the bend to let some air in, not sure if it will end up whistling for you. Or get rid of he last 90

 

[blaxsun]

Nitrates in the 5-15ppm range is generally the target for reef tanks.

 

[Fort Salty]

I reduced my return flow rate to alleviate the problem of filling and then siphoning empty like a toilet. I have a single drain pipe.

FS