FW tank to SW quarantine tank?

[fish are friends!!]

Hey....i was think of converting my 20 gallon freshwater tank into a quarantine tank for my (soon to arrive) saltwater tank should i? is it best to have a quarantine tank? would all i have to do is add salt? the tank currently has no fish, fake plants, and a fake log tunnel and 1 1/2 iches of gravel at the bottom. I know a lot of quarantine tanks dont have gravel or decorations so would i have to clean it all out? or could i just take out the tunnel in the middel and the plants for more room and leave the gravel?
Thx

[FoMoCo Master Tech]

It's definitely important to have a quarantine tank. If I were in your shoes, I would ditch the gravel and the plants and go bare bottom. It's easier to remove uneaten food or fish waste without a substrate. You could leave the tunnel to be used as a place for the fish to hide. Before using it, you should give it a real good cleaning. A vinegar/water combo works well.

[fish are friends!!]

Ok thx
how many fish can be in the quarantine at a time? i know its a small tank so would i have to wait to get more fish if some are still in the tank?