I recently made a wet/dry filter. It also makes a loud gurgling (obnoxious) noise from the siphon tube in the back. I saw someone on YouTube that used plastic ties and put them inside the back siphon tube. I just made a loop with the ties and rest them on the top of the siphon tube. It has helped the noise alot! It seems to break the suction of the water going down the tube---I know that discription is terrible, just not sure how to word it. Unfortunately it seems like every few days I have to adjust the ties a bit. It also seems like if you have any water evaporation at all from your DT the sound is much worse. I've been topping off the tank daily. I am definately going to look into the durso standpip but the ties were a quick, temporary, and cheap fix for me. Good Luck.