Have a good read on here about how to set up a saltwater tank and in particular how to cycle it. Best thing to do is plenty of research! will it just be fish only? Or corals? I would suggest fish only to start until you get the hang of things. As a rule saltwater is a little more time consuming and can be expensive so patience is the key. Not sure about that filter but I would say you will need a power head too for water movement. Invest in a good sw
test kit and a refractometer for measuring salinity (hydrometers are in accurate) also research where you will get your water from, tap water is a no no I am afraid. You can buy ro
water or make your own... A single clown will be fine with perhaps another small fish along with your shrimp and crabs... Any other questions just ask!