Hi, I am currently working on setting up my first Saltwater aqarium, and I have some questions, I do have some experience as I currently have a 20 Gallon long, 75 Gallon, and 135 Gallon Aqarium and they are all Freshwater. First question is can I use a fluval hang on the back filter or do I need a special type of filter? Next question is can I use the same type of heater that I have on my other tanks, or do I need a certain type? My next question is how do I turn my aqarium to salt after I fill up my tank with treated, and safe tap water. One more question about the basics is how do I add coral and what substrate does Coral require. My final question is, if my tank is a 140 gallon, 60x18x30 can I keep a snowflake eel and a yellow tang, which are the main fish that got me interested in salt water. Thank you for all the help.