Did you cycle this tank before adding all those fish. How about a timeline. The tank was up for 8 years, then taken down.
How long was the tank down?
What was in the tank before it was taken down?
What did you re-use when you set it up again?
An ammonia level that high leads me to believe that the tank is going through a cycle. You need to remove all the fish and get them somewhere safe until the tank is cycled. If that is not an option you need to start preparing water to do 30% - 50% water changes every day until that ammonia is ZERO.
please post the following info:
What kind of Salt Mix do you use? Do you let it sit for 24hrs with a powerhead and heater to airate and mix fully?
Do you use RO
water? How do you Top Off evaporated water?
Sorry it's under these circumstances but...