New setup have questions!

I recently purchased arund 150LBS of cured live rock. It came from a tank that was downsized. It had been sitting in a vat after being removed a month ago. Seemed to be kept properly with circulation in the vat. The aquarist included the excess sand that was in the tank as well. It had been kept in closed buckets. I added the rock and reefscaped. THe aquarist I purchased the rock + sand from told me not to wash the old dead sand, but to simple add it to the tank becuase the ammonia will feed the bacteria on the rock. Now the problem I have is, this dark greenish blackness has settled in the tank and on the rock after adding this dead sand. I continously keep clouding the tank up and sturing this "greenish stuff" around in attempt to skim it out. I've done a 50% water change already imediate after I added the sand. How do I completly get rid of this? Its been like this for over a week now and doesn't seem to be getting better.
Ammonia reads about .50 MG
Nitrite reads 0 mg
Nitrate reads 12.5 MG
Salinity 1.023

I was going to wash the sand which I knew I shoul have, but the aquarist maintains tanks for a living. I figured he knew what he was talking about..

90 Gallon AGA RR
75 gallon per day RO/DI
Bubble Magus 100 Skimmer w/ mesh wheel
2 Koralia 4
20 Gallon sump / fuge
3-4in sandbed
150LBs Cured liverock

 

If you're starting from scratch here, and have no livestock in the tank yet, you might consider losing the sand altogether and adding new sand. Generally speaking the "nose knows."

Does your "new" setup smell badly? If so, chances are the black stuff is sulphur-based compounds borne of anaerobic conditions in the sand.

If you already have livestock and or corals, that's another story.

 

I completely disagree with, not Sparky, but the other aquarist. One to two inches of LS is really all you need. Replace it out. I would never add dead, used sand to an existing set up. Why? I have done it before. Wasn't good.

 

As have I. Wasn't good for me either. When you compare the benefits of adding already live sand from another tank, or new dry sand--IMO the potential downfalls of the former outweigh the time saved.

Dry sand will become live sand in due time; without the possibility of adding something you didn't mean to add.