A refractometer will ensure that you will have accurate salinity readings.
You will want a protein skimmer as it will remove gunk from the water column along with your weekly 10% water changes.
You wonít need a water conditioner. Tap water causes issues in saltwater setups. Youíll want to use ro
/do water, which you can make your own or maybe buy from your LFS
. This will also mean you wonít need nitrate pads as itíll be managed with the skimmer, water changes, and 0 tds
As for the QT tank, you wonít need one really. If you want a clownfish tank, you will only be able to House two in a system due to aggression. They can be the first and last put into the tank in one simple swing.