No; stay clear of Balas unless your looking into a...like...200(+ probably)gallon setup in the future. They get huge and like to be in schools.
If you want to go with larger Gouramis, depending on how many your looking to get, you'll want to go 30 + gallons. Also remember that larger Gouramis(specifically the Blues and Goldens(in my experience at least))tend to be rather aggressive(quite like their cousins the Bettas), so keep that in mind when putting several together.
For Blues and Goldens, I would suggest doing probably 4-5(one male and multiple females)if you want multiples, witch will require 50+ gallons I think.
Stay away from Kissing Gouramis, they get HUGE and aggressive(like...100+ gallon huge)
Pearls are a larger species that are a little less aggressive. A lot of people keep them successfully in pairs, and you could probably get away with a pair(male and female)or just one in a 30-40.
Moonlights, in my experience, are very sweet somewhat larger Gouramis...I've never kept more then one, but I had one in my 50 gallon community along with a Pearl and a variety of other fish and she was very docile. You could probably get away with a pair in a 30, or 3+ in a 40+.
If you want to stick with the 20 gallon, you could only do dwarfs, or maybe a single Moonlight, or even a single Paradise Fish(they're a type of Gourami, more or less) and perhaps a few corys to scuddle around the bottom, or a small school of neons.
Also, take a look into Sparkling Gouramis...they're quite small; you could even keep a few in just a ten gallon.
Now personally, I would steer clear of any Blue/Goldens all together....its up to you of course, and if you're prepare enough and do your research then go for it, but I find them to be very aggressive(had a blue that nearly took out my entire 50 gallon community back in the day before I knew better)and get pretty large, so they require quite a bit of space.
Do a lot of research on the different Gourami species and be careful when sexing them; unless you have a very large well-planted tank usually two males will start going at each other/one will bully the other persistently(mainly talking about Blues/Goldens here, but I'd be wary of two male Pearls....couldn't say about the Moonlights, but it never hurts o be safe.). If you want more then one, try and get one male and multiple females and make sure you have plenty of hiding places/plants/tank space for everyone.
Last edited by DragonFish; 08-25-2011 at 05:18 PM.