how to quiet this pipe

wrap it in insulation. either the pink panther stuff or foam insulation or you could add a valve at the end of the pipe to let it fill with water. the water will flow through the pipe instead of fallin out. catch what im saying

If the white flex pipe is 1.5", then bio-balls will fit inside of it. The water will trickle silently down the bio-balls. If it is smaller, just be creative with what will go in the pipe for the water to trickle down. An unrolled pot scrubber should do nicely. Just tie one end to some fishing line and then tie that to a plastic pen with the ink cartrige removed. Then feed the unrolled scrubbie into the pipe while water is flowing through it. Place the pen perpendicular to the exit bulkhead to keep it from going down the drain. The pen and string will prevent the scrubbie from bunching up at the bottom 90.

Tha Bait Shack uses bio-balls to quiet a 6ft drop, and my 250g uses plastic netting (similar to an unrolled scrubbie) for a 2.5ft drop. The only issue I had was snail shells building up in the bio-balls. The netting turned out to be self cleaning. It also moves out of the way when something large goes down the shute.

Another way of quieting it is to install a ball valve in the bottom pipe. Then close the valve just to the point that water backs up in the pipe, reducing the noise. You can use the valve to cause the water to back up in the pipe so that it is entirely full if you wanted to.

The flow will be self regulating because as the water level in the pipe increases, the more flow you will have. If there is a surge in flow into the filter, the water level will rise temporarily (increasing the flow) until it equalizes again. At first, you will need to tweak it to find where you like it best.

Slowing the flow is the whole point. That is why it sounds like Niagra Falls (speed plus air ingestion).

Right now your pipe is capable of flowing more water than is actually going through it. By adding a valve, you are tuning the pipe to the actual flow. When they are the same, the pipe will not gurgle or sound like a water fall.