Questions new-ish tank. Grey Spots

[travischristy]

Hey All,
I have some questions regarding my tank. I am new to saltwater and I have a 100G that has been up for just 3 weeks. Here's what is in the tank:
-Live Rock (60 lbs)
-80 lbs of Aragonite Sand on top of 80lbs of Silica Sand
-1 Scoop of Live Sand (~1lb)
-10 Hermit Crabs
-1 Snail that found it's way into my tank with live rock
-1 Clown Fish I bought to test living conditions
Everything in the tank is alive still except 1 hermit. I went on vacation and left a very small "Vacation Time-release" piece of food in the tank. When I came home, I noticed a few differences in the tank that got me concerned:
-Dark Grey spots on substrate (aren't diatoms supposed to be brown?)
-Tiny White spots/rings on back of tank and a few rocks (snail eggs? they are rings so idk)
-Small Sand-colored lines running along rocks (hermit poop?)
-Presence of tiny critters running on and around rocks
-Clown fish wont eat mysis shrimp or other food
I don't know if I should be concerned about some of these issues and take action, or should I just let them resolve themselves? I'm going to post pictures (below) of the things concerning me. Thanks for your help!

 

[mr. limpid]

i apologize no one responded to you and that I'm late, but better late than never. first your tank is very young it cycling and allot of changes will happen in your tank for next couple of weeks. you need to get some test kits for ammonia , nitrates and PH these are the basics. Do not add anymore fish or critters until your ammonia and nitrates read 0. I will try to answer your questions dark gray spots on sand, start of algae bloom it will get worse before it gets better. Tiny white spots could be copods eggs good thing. Lines of color in sand could more algae. Tiny critters on rocks copods good thing natural food for fish and hermits. Clown fish wont eat mysis shrimp or other food. Did he eat at the store? If he did try feed same food, still offer other types. If all else fails try live brian shrimp, but still ween him off it not good for long term. Good luck