Which hang-on-back filter is actually quiet enough to sit two metres from a bed? Aquarium

Before you replace it: pull the impeller, check the shaft for a hairline crack, and check the rubber bushings at each end. A cracked impeller shaft is the single most common cause of the exact symptom you describe, intermittent buzz that goes away when you nudge the housing. Impellers are usually under $15 and it is worth ruling out before spending $70.

Different suggestion since you have plants: a large sponge filter on a decent air pump. In a planted 29 the plants are doing most of the nitrate work anyway and you do not need 6x turnover. The catch is the air pump becomes the noise source, so you put it on foam too, or below the tank so the diaphragm hum has nothing to resonate against.

I run two hang-on-backs on bedroom tanks and the quiet one is quiet because of how it is mounted, not because of the badge. Both sit on a strip of dense foam between the bracket and the rim, which kills the buzz transmitted into the glass, and the glass is what actually makes the noise loud. A $3 offcut of yoga mat did more for me than any filter swap.

Terse version: any hang-on-back is quiet for the first year and noisy after, unless you clean the impeller well quarterly. Put it in the calendar and the filter question mostly goes away.

I went through this last winter and ended up moving the tank rather than changing the filter. Two metres from the bed against a hollow stud wall is worst case, because the wall becomes a speaker. Same filter on the opposite wall, which is masonry, is inaudible with the door shut.