One quiet trick
My Fluval 205 was a bit noisy, not due to the filter directly but due to a resonance in the wall and stand floor.
I have an inline heater and some stiffer than standard tubing to it. This was transmitting some vibration from the filter to the wall behind the tank, producing a low hum. It was actually louder in the bedroom on the other side of the wall than in the aquarium room.
I used a few zip ties to hold the heater against the stand and off the wall, instantly much quieter. Next I put a small piece of carpet under the filter between it and the rather flimsy bottom shelf of my stand. All noise gone!
29G - ReefKeeper Lite Controller - Pressurized CO2 - Hydor Inline heater - Fluval 205 - Fluval Pimp #18