Sieve cleaners (1) for cleaning a sieve surface (2) of a sieve box (3), which sieve box contains a sieve surface (2) and bottom (4). The sieve cleaners (1) contain a wobble foot (5), which extends along a main axis (A) of the sieve cleaner (1) and is designed such that the wobble foot can be placed onto the sieve bottom (4) and the sieve cleaner (1) can be tipped about the wobble foot (5). At least one cleaning element (6) has a cleaning region (7), and each cleaning region (7) has a plurality of cleaning surfaces (8) for cleaning the sieve surface (2). The cleaning surfaces (8) are each designed for at least linear contact with the sieve surface (2) and are separated from one another by slots (9) formed in the cleaning region (7). Sieve units and methods for upgrading or converting a sieve box are also disclosed.