I would agree with Birdy about the worms and infauna being more benificial to a dsb. IMO snails do a better job as far as a cleanup crew, so if hermits are not available stick with snails. Conches are good sand cleaners. Also, someone correct me if I am wrong, but a sand siftiing goby may do harm to the dsb, as it will deplete the benificial critters in your sand bed.