Originally Posted by ChizerBunoi
Oh just realized that it was your bubbler in the middle. That output on the right corner shouldn't be making any noise. Maybe it's your powerhead? Did you invert it inside the tank to get all the air out of the propellers?
The noise is made by the "drain" on the right - when the water goes down into the hole; does that mean that there should be more water going through there? I see the current in there is quite strong.
When I reduced the diameter of the hole the noise was significantly smaller-- I don't know whether I can do that on a longer term?