A frag tank is just like a display tank, except you're not mounting corals to make a decorative display, you're just putting them on egg crate to grow them out. You can go bare bones with a fish QT tank, but you really need proper equipment to grow corals out.Think about it like this, if you need a piece of equipment to get things to work well in your display tank, you'll likely need it in your frag tank. All the really nice frags tanks I've seen are essentially regular reef tanks in terms of their setup.