http://m.**************.com/product/prod_display.cfm?pcatid=28052
Something like this. You just run an airline hooked up to an air pump into it and that causes flow through the sponge. Great for bio filtration.
I ask about what is included because for salt water we typically don't use the same thing that would be included in a kit. closed hoods it inhibits oxygen getting into the water so we don't often use them. Egg crate (light diffuser) or screen tops are pretty common to prevent jumpers from escaping.
The lighting in a typical aquarium kit isn't what you'd want for salt water. It wouldn't hurt for fish only but tends to look bad, kind of yellow. That is where I started and ended up buying new stuff that cost more in the long run.
If a stand is included that may make a difference in price that makes the kit worth it. Otherwise it may be more economical to purchase the 40 at the dollar a gallon sale and buy a LED light fixture separately. SB reef lights has fixtures that aren't too pricy (I've heard good things about them) but give you control of the color of the lights.
https://sbreeflights.com/sbox-reef-lights/1-sbox-basic.html. Just something to consider.
A lot of us build our own stands. For me the typical stand is too low to view comfortably and there isn't enough clearance in the cabinet for equipment inside a sump. There are plans on some of the bigger forums for DIY stands. They are very sturdy and economical.