Is it the tank containing these - 6 neon tetras, 1 male swordtail, 1 emerald green cory cat, 1 dwarf pleco ?
If so, I'd first concentrating on getting a few more cories (is it a
Brochis?). Also, what kind of 'dwarf pleco' do you have? How big will it get?
My concern is that you only have a limmited volume left for some gouramies so all depends on the potential size of the fish you already have and the species of gourami you're interested in.
Let me first say that it would be best to avoid three-spot gouramies for a community set-up. They are particularly territorial and can be extremely aggressive towards each other and other fish (especialy when breeding - which is surprisingly often because they are one of the easiest gouramies to spawn). I'd also avoid anything that grows quite large such as kissing gouramies (which would probably eat your neons and are quite territorial anyway) or moonlight gouramies (which are peaceful but need more room than will probably be left in your tank).
The previous poster mentioned pearl gouramies - these are my favourite fish and wonderful community inhabitants. Deffinately look these up and see what you think of them. I think there's a nice profile with beautiful pics in the fish index section. They grow to about 4-5". males are slightly larger, develop extended fin rays and a bright red-orange ventral coloration and have longer fins. They are realy one of the easiest gouramies to sex, IMO the most social and certainly one of the most peaceful. The downside mainly is that they
can be prone to being nipped (though the fish you have at the moment should be fine) and I wouldn't keep one singly - a trio (1 male, 2 females) or a small group of females works best.
A similarly-sized alternatvie would be
Colisa fasciata (banded/indian/striped/giant gourami) or
Colisa labiosa (thick-lipped gourami). The former grows to 4", the latter to 3.5" or so. Both look similar to the familiar dwarf gourami (
Colisa lalia) but are far hardier and seem slightly less territorial. Either of these would do well as a trio (as with the pearls) but you can also keep a male singly if you don't want 3. Males are more brightly colored than females and have longer and more pointed fins in both species when compaired to females. Another useful trick is to look at them from above - the females are wider than the slimmer males.
If you want something small but equaly beautiful and peaceful, I highly reccomend honey gouramies (
Colisa chuna/sota) but take care not to confuse them with the dwarf gourami as dwarfs are very prone to disease (and therefor liable to introduce disease into an established tank unless quarantined). Honeys grow to about 1.5" with males typically being slightly larger than females. Males also turn a beautiful blue-black on the bottom half of their body when in breeding condition. There are a handful fo color morphs - IMO the wild-type is the most beautiful 9especialy when in good condition) and they are also hardier than the heavily bred 'artificial' morphs. Again, a trio works well but they could also be kept comfortably in a larger group as long as the number of females outnumbered the males as their small size means they won't be competing as much over territory as some of the larger fish.
All the above are mainly top-dwelling species that like to stay nearer to the surface of the water. As such, they are ideal for a tank like yours that contains quite a few lower to mid-dwelling species. They also all like to have floating or very tall-growing plants to mark out territories and to make them feel safe. Without these, they are often shy fish and will spend a lot of time hiding. Of the afformentioned species, the banded is probably the best suited to a tank without as much planting but still needs some to be active and to thrive. Though the males, in particular, of all these species are territorial and will drive away other fish (if they've built a bubblenest), most aggression amongst gouramies is directed towards their own kind and, with the above species at least, it is quite mild and shouldn't disturb the tank. The space occupied by their territory also tends to be small and near the surface (though floating plants help to make this the case) so it's not something that should be a problem. Note, however, that a strong current will not allow them to establish a territory near the surface and this can pose problems (more so for the gourami itself than for the other tank inhabitants though). So make shure the flow is not very strong or, alternatively, make shure you ahve some of those floating plants
There are also species of gourami that spend more time lower down in the water layers - croaking gouramies (
Trichopsis vittatus) and sparkling gouramies (
Trichopsis pumilus) are a couple of the hardiest and most common. However, they are not the most brightly colored and are difficult to sex. Because it is difficult to establish which fish are male and which female, they may not be ideal for a peaceful community unless you are prepaired to buy a bunch and, when they are mature, pick out any that are clearly male and return all but one. The problem is that, unless the number of females is large and the planting heavy, males often will fight amongst each other. This isn't a problem for other fish - but it is for the gouramies themselves. Sparklers barely grow to over 1.5" but truly do sparkle and croakers get to about 2-2.5" and have beautiful fins and blue eyes. Croakers are so named because they will 'sing' when fighting, displaying or spawning. It's an amazing thing to hear and is mainly done by males.
edit: I should add that when I said 'three-spot' at the beginning, I was reffering to
Trichogaster trichopterus which has many color morphs including gold, blue, opaline, cosby, platinum and lavender (a couple were mentioned by previous posters). These grow to 6" and, while a group of females works in a community setting (because most female gouramies are not territorial), males will often fight to the death like bettas and are very territorial. A male/female group will almost inevitably spawn - in which case aggression can become intolerable for even bottom-dwelling species such as cories. Unfortunately, the territorial males also often posess a larger territory than some of the mroe peaceful gourami species. The upside to these fish is their beauty (especialy the males who have longer and more pointed fins) and there incredibly hardy nature.
Sorry about the length BTW - didn't realise until I looked at what I've written just now lol
