Quick question about Pico reef filtration

I am setting up my second pico reef tank. The first was a 4 gallon Aqueon Evolve that I had to break down due to my lack of time that I had to commit to it. Now that I have more time on my hands I want to set up a 5.5 gallon tank. I already have the tank, LR, and LS. I also have a heater and a decent light. My question though was what is the best method of filtration for a tank this size?

 

This tank has a back chamber with an over flow?

If that is the case, a simple sponge for mechanical filtration and chemipure elite for chemical filtration. The rock/substrate and sponge will take care of your biological filtration.

Consider an automatic top off device.

 

The Aqueon does have the back chamber, but my 5.5 is just a standard tank. I went with an AC30 that I put the sponge and carbon in it because I couldn't find chemipure.