Renewing Substrate

R Murri

New member
I have had a 90 gal tank set up for almost two years with a 3 inch substrate of mixed small shell, crushed shell, sugar fine and larger aragonite, gravel sized reef rock,etc. I inherited it when I bought the tank set-up.
Anyway, in the last few months I have noticed a lack of 'critters' in the bed. I used to see tunnels and tracks in the bed. Now I don't. Also, I have done a 2 am expedition with a red lens flashlight and see no pods and very few tiny snails, which I used to see.
I have two Saddleback Clowns, a Yellow Tang and a Coral Beauty for fish, and maybe ten small hermits , and maybe a dozen snails. I wouldn't think these would deplete the bed, so
I am curious to know what may have happened and if there is a way to renew the bed?