Yes - this is a pico. Picos are very difficult to keep stable. It's a bad choice unless you have quite a bit of experience with other marine tanks already.
Asking this question with such a small tank is really starting out on the wrong foot. The general beginner rule is that fish do not belong in a pico. There are exceptions to be found on the web with some of the really small goby species, but those are expert-level endeavors. If you are primarily interested in fish, you need to be looking at a much larger tank, such as 30gal+. 50gal is considered a good starting size in marine. The smaller you go, the harder it gets.