1) I have a small tank and crushed shells substrate (purchased from a pet store for this purpose). I want to clean or sterilize the tank and substrate before assembling my tank and adding the brackish water. What's the best way to do this? Do I need to use distilled water to clean and soak the substrate? I saw that I should not use any kind of soap, so I will definitely avoid that.
2) What is the recommended brand of fish food for feeding? I've seen people mention a "high quality" brand, but being new to this I have no idea what is considered high quality!
3) If I buy or find some dead coral to place inside the tank, what is the best way of cleaning it to ensure that it will not cause ammonia spikes or other imbalances?
4) Do you absolutely need to have a light? I plan to keep my tank on my desk which receives a lot of natural, indirect sunlight throughout the day. I would prefer not to have one, but maybe it's more important in the winter?
5) Any other tips or tricks for a total newbie? I'd appreciate any insider information not already listed on the info page here!

Thanks for your time!