ACk, SpS's with colour, I can't find any....

[Der_Iron_Chef]

For maintaining a reef aquarium--in particular an SPS-dominated reef aquarium--the water quality must be very high. Dissolved organic waste (aka-fish poop) will not be filtered out by the type of filter you are describing.

It's definitely possible to have a 5G "pico" like you're describing, but I think it would be difficult, especially for someone just beginning saltwater. The ability for something very small (a snail dying) to foul up a 5G aquarium is very strong. Things can go bad in a hurry and there is very little water to absorb whatever it is.

That said, if you still want to make the effort, it IS possible....but I would recommend asking a lot more questions and doing a lot more research first. After all, these are living creatures we are talking about! We don't want to kill anything, if we can help it.