Smelly tank

[Coralgurl]

I appreciate the help, thank you!

Tank size posted above but it's 180 plus 80 gl sump. Have a reef octopus 5000 skimmer, 2 mp 40s. Approximate 140 lbs of live rock.

Bioload
2 clowns
Bangaii cardinal
Royal gramma
Solar wrasse
Radiant wrasse
Hippo tang

20 sand snails
30 reg snails
Approximate 5 hermits

Mix of lps corals, toad stool, mushrooms, zoos.
Transferred tank on march 5 from my 55 gl after cycle. All fish and corals look good. Sand has been looking dirty for just over a week which is why I added the sand snails and starfish. It's been getting worse over the past 2 days.