Just did a little number crunching, and it looks like that is 18.8 U.S. gallons. That is a good size to start out with as most people getting into the hobby start with much smaller tanks and are discouraged because they cannot get the fish they wanted. This tank can accomodate many different combinations
of fish, but here are a few off the top of my head.
Stocking 1: 1 Dwarf Gourami, 12 smaller Tetras (Glowlight, Neon, etc.), 5 Bottom Feeders (Kuhli Loaches, Ghost Shrimp, Smaller Cory Cats)
Stocking 2: 3 Guppies (all males), 2 German Blue Rams, 8 smaller tetras
Like I said, there are various possibilites so these are just two out of hundreds of other options you have.