Newbie here with some questions about my cycling tank

[Sumfingwong]

I have recently converted my 65g to salt about 1.5 weeks ago.
I am using:

- eheim cannister filter (2 days ago I packed it full of carbon, before that there was ceramic and bio balls for my freshwater setup)
- Aquamedic Turboflotor. I only turn it on when im home during the break in period.
- I added 15 lbs originally with cured/cycled LR from a LFS. 4 days later, I picked up another 8 lbs of live rock from another LFS. The LR was from a display tank, so it was packed with coraline algae and hitchhikers (1 crab, 3 hermit crabs)
- I added 3 yellowtail damsels this past sunday to help with the cycle

I have been feeding the damsels with flake food, and I also noticed when I picked up the first LR, there must have been a crab, because I found a claw floating at the water line.. and the body of the crab is at the bottom of my tank. I figure I would leave the body so it can add to the ammonia to kick start the cycle.

im also beginning to see the brown algae (which I have read to be a good sign of a cycle) Actually, its just brownish stuff hanging off the LR, so I am assuming its the brown algae.

The latest readings were
ammonia - 0
nitrite - 0 ppm
nitrate - 5

With these readings what does it mean? The tank is only 1.5 weeks old, would I be getting nitrate this fast? Was the LR I picked up recently packed with so much bacteria, my tank didnt go through a proper cycle?