Nasty beige sump.

[Miami Reef]

What is this called, and is it a problem?

Should I scrub down my sump?

 

[EuphylliaAddict]

Detritus, I would syphon it out the best you can on a monthly basis, It reminds me that I need to do the same. It's just sand particles and such that made it past the filter socks, detritus, I added wave makers to these compartments to keep that stuff suspended. I would just syphon it often though to keep it clean.

 

[HD_Reefer]

Detritus. Yes, clean it out. Also, you may want to replace the clear flex tubing while you're at it, there's already algae build up visible inside them.

 

[nereefpat]

If it bugs you, clean it. Otherwise, you don't have to. That stuff is mostly inert. Some people use a shop vac.