I am very new to fish keeping. I bought a tank a week ago and didn't really do any research before I started. I listened to the girl at

Today I went and bought 2 Dwarf Gouramis and a Pleco. I did research before I bought these and every where I read said they would do fine with the sharks. This may sound far fetched, but the sharks are not the problem, the gouramis are fighting each other. I sat and watched them fight for a couple of minutes today before I tapped on the glass to make them stop. They are ripping each other's fins up. Not severely, but they are torn nonetheless. All the pages online say they are none aggressive and make good community fish, and get along with the sharks. The sharks are actually steering clear of them because the gourami are a lot bigger than the sharks. (for now) And the pleco is just hanging out sucking on the sides of the tank.
Has anyone here ever had any experience with their D Gouramis fighting?
BTW, I have them all in just a 20 gal tank. For now they have plenty of room as they are all small, but I know that I will have to either give some away soon or buy a much bigger tank. The sharks were my DH's idea. I had already picked out much smaller fish to start with, but well you know how husbands can be when they don't get their way. TIA for any help.