1. The power heads can be quite noisy if the power chords chater against the trim that cover the channel across the top of the tank. Lift the hood and put you finger on each chord - if it quietens, you need to move the chord one way or the other so that it doesn't chatter. If it has no effect put your finger on each of the pumps - if it quietens, you need to make sure the nozzle holding it on is tight, and that the two pumps are perfectly upright - if they touch, they wil be noisy. They will also become quieter as the slime coat grows inside them (acts as a lubricant)
2. Most people I know have taken the grey knob right out - but if your skimmer cup fills with water you'll need to screw it down until the foamy bubbles stop just below the top of the cone in the removable cup
3. It will probably take any marine flesh - shrimps, fish, whatever - they'll even take freeze dried crickets - just don't overfeed it.