If you've never set up a marine tank before, this is going to be very difficult. I studied marine tanks scrutinizingly as a hobby for over 5 years without ever setting one up. That included nearly weekly visits to my saltwater specialty lfs whose owner was impressed at my knowledge and said that if anyone could pull off a nice pico reef it would be me. I dropped nearly $500 in trying to get it right and everything worked except the acclimation and constant water parameters. It's very difficult to either float a bag or rig up a drip system for a pico especially when you only have 3 gallons to drip from. Then after getting acclimated, they have to adjust to major salinity swings even if just half a centimeter evaporates off. If I ever attempt a pico reef again (which I will when I have money I'm willing to throw at it) I will hook up my 20g tall as the sump underneath so there is more volume and less room for swinging parameters. Also there'll be less junk clamped to the tank. Best of luck though.