How to clean Sump?

[Spyd]

First off, be very careful not to disturb your DSB too much. It can potentially releases toxic gases that build up over time.

I would just turn off your return pump and skim the top layer of sand with a fine fish net.

If you want to give your entire sump a good cleaning, drain it all, minus the DSB, remove all equipment and wipe it down. I find a Chamois works well for getting that last 1/4" of water out and wiping down the compartments. Add freshly mixed saltwater back in the sump and you are good to go. Very timely process though.