If I have fish already in the tank, I usually let it run through my filter and it cleans it up within 24 hours.
If I don't have fish in the tank, I opt to do water changes. This worked well when I set up a new tank and there were no fish in there, so nothing to disturb. I put water in a few inches above sand, stirred the life out of it, let the sand settle and vaccuumed water out. I did this about 5 times. It was time consuming but made a huge difference.
No matter how you do it, be sure to rinse all of your filter components (including housing) about a week later to remove all the sand.
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~