Just a few questions

[BigMike81]

I have some questions regarding some equipment that is not used in fresh water tank. What is a refugium, what is a sump and what does it do. And what type of filters are good for a 75g tank?

 

[Reefing Madness]

You can use the same filters from a FW tank in a SW tank if you wanted to. They are not really necessary though, thats up to you.
How does a sump work? | Melev's Reef
Everything You Always Wanted to Know About Sumps, Part I by Greg Taylor - Reefkeeping.com
Reefkeeping 101 – Sumps! by Marc Levenson - Reefkeeping.com

 

[dasteve003]

I believe a refugium is a separate tank hooked into your tank that can have slower flow for plants and animals that need it. I'm not 100% sure but I believe that's the jist of it.