1. How often are water-changes required for this size tank?
I would recommend weekly but it will depend on your bio load and coral choices. I would say half a gallon a week or 1 gallon every two weeks.
2. What is the best method/procedure for actually removing the water during a change?
Shut all pumps, syphon out the desired amount with a small tube into a container and replace with new salt water. I would add the fresh water slowly - you want to make sure it doesn't splash or upset the /corals when replacing water.
I use to poor it right into the rear filter of the edge and let it drain down as if the filter was on.
Remember - Make sure the water has correct salinity and temp.
3. Best method for making sea water (add salt mix to ro water)?
Myself and other nano owners that I know buy the pre made saltwater from petco. There are a few brands out there and i believe they are all the same. It works great, Just heat it up and add.
The pre made saltwater is perfect for nanos. I get roughly 4 water changes out of a box over the course of 4 weeks. Many people use it. Some people advise against it because it gets pricey with larger volume aquariums.
(I have been using it almost 3 years)
Top off with distilled.
4. When cycling a tank, do I cycle with just live rock, or cycle with rock and live sand?
Cycle with sand and Rock.
When setting up:
Add rock, then sand, then water. It will become cloudy. You can avoid this by placing a bag (like a small ziplock bag or plastic bag on the bottom and pouring the water into that and let it gently overflow till it's filled.
5. Recommended source/brand for live sand?
You can really use any sand that's sold in stores. You don't need
Much so you can just buy a bag of that livesand they sell. With larger tanks some people avoid buying the live sand because it can get pricey. Again, in a nano it doesn't matter!
I would avoid the sugar sand they sell at petco. It's a mess!
6. Recommended thermometer?
You could go with one of those digital ones for now but most people would suggest going with a Controller. Something like a reef keeper lite or
apex etc ( there's a few good brands)
7. Lastly, I live in Manhattan: recommend fish store within an hour?
Manhattan aquariums is great. It's on 37 and 11th I think.
Plenty of vendors on here to get livestock and equipment. And they don't mind answering questions!
Some suggestions
Check out picod's edge. (search for her thread)
Check out nano-reef.com (Nanos! Nanos!)
Use what others have had success with. An edge can be tough once stocked. (any nano can be)
Always have extra water premade. (that's why premade box water is great)
Good luck and take it slow.