Help Brown Diatom

[GinKu]

hi guys
i don't know how to get rid of them what do i need to do to get rid of them?
i have had this for about 1 week now and i haven't down nething except mix the top layer of the sand to get rid of it
all i have in the tank right now is 1 false percula , fire fish, 2 turbo snails, and 5 blue hermit crabs 5 red scarlet.
what should i do
i might be getting some more red scarlet crabs this week
suggestions?

oh ya my tank is 90 gallon tank with 30 gallon sump