A stony coral is any hard coral that has a calcium based skeleton. This group is further divided into LPS
(Large Polyp Stony Coral) and SPS
(Small Polyp Stony corals). SPS
are much needier than their LPS
cousins. They usually require much more flow and more light. an example of LPS
would be a Hammer Coral. Acros are SPS
etc. Take a look at Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
for more info/pictures.
As for a reef salt, it's up to you. I used to use Instant Ocean Reef Crystals but it just didn't go very far. The box of salt for 200gallons only makes 200gallons if you're mixing your salt at 1.21 Salinity. It's best to keep it at 1.26 for a healthy tank. I'm currently using Salinty by Aquavitro. So far so good. It's got a bit more Ca
than IO Reef. But I basically use it because it's a better deal at my LFS
and it comes in a large 225g size (@1.26 salinity). It'll last me much longer.
But you really should do some research and find what' salt is good for your needs.