Yes regular plastic pot scrubbers and yeah dollar stores should have 'em although I've always ended up getting them shipped 'cos I use them in larger quantities and finding dollar stores by me that have 'em has been frustrating.
IMO you won't need 'em day 1 as the sponges and ceramic should get you where you need to be but it won't hurt to have more space for bacteria to populate going forward.
IMO you won't need 'em day 1 as the sponges and ceramic should get you where you need to be but it won't hurt to have more space for bacteria to populate going forward.