I have 2 three spot gouramis and the warnings about size are so important. When I first bought the pair no one told me how big they'd get. They were about 4 cm long each and I put them in a 45 liter tank. They were fine in there for about a month but by then they had already grown to a bit over 5 cm each and were chasing one another all over the tank. I moved them to a 95 L tank where they now live with a pleco and 5 black-skirt tetras. These are beautiful, visually appealing fish that I never get tired of watching. To see a real feeding frenzy, dump some live brine shrimp in the tank. My boys had a real party with those and now they don't want to eat anything that doesn't swim on its own. Gouramis have quickly become my favorite fish and in addition to my 3-spot boys in the larger tank, I also have 3 dwarf gouramis in my smaller tank. If you can provide them with the space I highly recommend these wonderful fish.
If you plan to breed this fish, have one male to a few females (4-5). When the male chooses his mate (you will know this when he chases her around), remove them to the breeding tank, or remove the others. Make sure the tank is well planted with hiding spots and floating plants. The male will build his bubble nest and have the female release her eggs by squeezing her. Sometimes, if the female tries to help, the male will harm or kill her because he is jealous, so have a hiding place or remove her after laying the eggs. When they hatch, the male will care for them. Feed the fry grounded flakes or other food. Be careful or they may find themselves into a stomach. It is not uncommon for the fry to die young. Good Luck :-)
I used to have a male three spot gourami and we called him Hitler because being new to the hobby I purchased one of these with some dwarf gouramis and put them into a peaceful community 40 Liter tank, he dominated the whole tank and sent all the fish into hiding except to careless tiger barbs who just ran when they saw him, well eventually they all died except the barbs because he starved them one at a time, he was especially mean to the dwarf gouramies. After all that happened before he could bug the barbs, which I think were too fast for him anyway, I moved him into my 100 Liter cichlid tank and he's about 13 cm. The oscar (12 cm) doesn't even mess with him, he's happy there but he is certainly no longer the tank dominator..
I have two of these gouramis, one Big Blue is several years old and about 15 cm long, the other is very new to the tank and about 8 cm long. I have found them to be very peaceful fish, they only defend themselves against my cichlids. It's not their fault that they are very good at defending themselves. My rams and parrot fish usualy end up limping away after a confrontation. As far as plants I have amazon swords and have found that if I feed the gouramis algae discs then they leave my plants alone. They don't hide in the tank and are always right in the middle, the first thing you see when you look at the tank.
My two Blue Gouramis turned out to be males, and you can often catch one sucking at the other's sides or tail and chasing the poor "victim" around the tank. They never harm each other, more like pester a bit. They are voracious eaters and usually eat up most of the food I offer at feedings. I've also noticed that their colors change with mood - when slightly surprised or irritated, their backs start to darken - very interesting to watch. They are peaceful fish and do not bother the rest, only themselves.
I had one of these fish in the first freshwater tank I ever started. I purchased it to look good along side the Golden Gourami I had then. If either were agressive, I'd say the blue one was; he was also the larger of the two. This fish chased Goldfish but didn't do them any harm and did not bother with any other fish at all. As I was inexperienced with fish at that time I did not know I was buying a sick fish when I added the Lionhead I found; unable to control the Ich in time, I lost every single fish in that tank except this Blue Gourami. He remains one of the healthiest, strongest fish I've ever had. Confident in his survival skills, I have named him The Big Blue Meanie (affectionately, of course).