From tropical to cold water fish tank


Small Fish
Mar 20, 2011
I wonder if anyone could help me.
I am up garding my goldfish to a second hand tank I bought its 4ft but was a tropical tank. I wonder if it is safe to use for my goldfish? It has been dry for 2mths & comes with the gravel & enheim external filter (huge) with all sponges.
Do I have to get new sponges?
Can I reuse the gravel?
Is there anything bad in the tank because it was once tropical that can harm my goldfish?
Also how long will it take to cycle till its safe to add the fish? Can i reuse the tropical sponges for this as my xponges are too tiny.
Any help would be grately appreciated.