Just set up a 75 gal with a 30 gal sump. In the process of cycling it now. In the meantime I set up a 27 gal qt for 2 small clowns with a HOB filter and a large sponge and added about 4 oz of turbo start. Wasn’t gonna use a substrate but had a couple bags of black FW aquarium gravel. So I added that as to help give the bacteria a place to occupy. Is that gravel ok to use in a salt water system? Clowns are on their second day in the qt system and doing great so far. Were very healthy to begin with and started eating right away and moving about the tank as would be expected. Thank for any advice.