Super quiet skimmer and return pump

[Jakegr]

I'm using a Sicce Syncra right now and IMO it's kind of noisy compared to the DC pumps I have used (Reef Octopus DC and a waveline DC). The reef octopus has a subtle high pitched whine, but it is definitely a lot quieter than the Sicce Syncra.

Choosing the smallest possible return pump for your tank is another way to minimize noise.