I use a good old aquarium vacuum on my sump and fuge to clean the detritus out.
But I would guess that is not the sole source of your nitrates. To get 'trates to zero you need to do a lot of things like:
- Have Good flow
- setup Fuge with macro-algae
- Regular water changes
- Don't overstock
- Use RO or distilled water for change outs and topoff
- Aquascape rock so detritus cannot get trapped in a corner or hole
- Do not over feed
- etc.
Whenever I'm about to do a water change, I take a turkey baster and blow the crap around before I start the siphon.
I just use some 1/4" airline tubing, start a siphon, and suction it out.
I know. But the sump is on the ground. It's too low to keep it going