I have three tanks
10gallon : two (separated) bettas
30gallon: Green Spotted Puffer (Milton) Brackish
55gallon: Salt Water, live rock only
Patience and lots of water changes are in your future.
In the Saltwater tank :
Yellow Watchman Goby
Fake Plants in the Brackish and no Corals (yet!)
I go to the Art Institute for Graphic Design
When you see signs of stress in your fish, you can then take steps to identify the source of that stress and then to resolve it before it becomes a major issue.
If you're looking for a unique way to stock your new tank, give freshwater shrimp a try.
If your fish is suffering, you may want to consider euthanasia as an option to humanely end his pain.