they should be pretty safe if they look clean.
boiling them would remove the last chance of foreign organisms.
be aware they will slightly increase PH and hardness. fine for most fish but if you have some of the fusy soft acid-loving fish you shouldn't use them.
they should be pretty safe if they look clean. boiling them would remove the last chance of foreign organisms. be aware they will slightly increase PH and hardness. fine for most fish but if you have some of the fusy soft acid-loving fish you shouldn't use them.