I don't - both tank and sump are BB in my 190. In my 230 I have a DSB in my tank and Miracle Mud in my sump. Just a whole whack of live rock in all sumps.
Personally I find the sand or mud in the sump is harder to maintain because mine is on the floor so I can't siphon - I guess I should buy a wet vac one of these days and suck some of the mud out of there and replace it with fresh. It's just over a year old now.
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