6lb rock in a 40 is really not enough but its a start
since its still easy to remove the rock with cayno you can remove it place in 5 gal bucket filled with a gal of salt water scrub it with a tooth brush than rinse in another clean bucket of salt water than you can place it back in your tank prob still do a 10% water change to help rid any contaminants in the tank
since its still easy to remove the rock with cayno you can remove it place in 5 gal bucket filled with a gal of salt water scrub it with a tooth brush than rinse in another clean bucket of salt water than you can place it back in your tank prob still do a 10% water change to help rid any contaminants in the tank