Good because I wanted to warn against assuming that all gouramis are community suited, even all dwarf gouramis. If they were, it would be difficult to explain the number of aggressive-gourami-posts that the anabantoid forum gets through in a month! "Most species will cohabit with one another" is not every gourami keeper's experience. The main point about gouramis is that they are territorial. This goes for dwarfs too, though you do find some dwarfs that are mainly timid, some that are laidback (and a lot that are too sick to do anything much). Still, if you want to risk the health hazard with dwarfs, then a Rio 300 probably is big enough to allow for two territories. Or, you could aim at keeping a large enough group so they can't establish a territory at all. At least you've got a bit of space to play around with.
Golden/opaline/blue gouramis are well known for being territorial and can get very aggressive about it.
If you want many gouramis a group of pearls would be a good option. They are healthier than the dwarfs, more peaceful than the opaline, and to IMO they are the most elegant looking fish you can find.
