Black stuff in fermenter, mold?

That looks pretty awful. Does it have a smell or a taste to it?

 

Not going to say you didn't do a good job cleaning, but I feel like the first few times you use a new stainless steel vessel it always seems "dirty". My two trials with my new brew kettle where like this. First time it looked like a yellow is film came off, and the second I had another film that seemed to come out at the end of my trial. Can't say you are seeing a similar thing, but it is just an observation of mine.

 

I have no idea if it's dangerous or not (I'm guessing not), but when I first received my stainless steel brew kettle, I did a boil with plain water at the advice of people on a different thread in these forums. It did indeed seem to remove some sort of manufacturing film off of the inside of the pot, as there was slightly different colored-finish to the area that was touched by the boil water.

 

At what concentration? The instructions say way more concentrated than normal StarSan solution.

 

I thought it might be your etch marks, but your pix shows that they seem to be intact.

 

If it is what I think it is (a slight oxidation of the surface treatment) then it should be OK. I forget what it is exactly but the way they shine the SS will oxidize and falls out visibly. After the first few cleanings/uses should stop happening. SS cleaners are suggest to be used to help make sure it happens from the get go. It was part of the reason I did 3 boils with just water with my new kettle, although the first one kind of scared me.

All said and done, at worst it should mostly be in the trub at the bottom of the fermentor.