I do not have a lot of gourami experience. I only kept them in my very first tank and then for under 2 years. From what I can read on the sites where I go for info on fish it would appear it could work but that the gourami would likely want a tank with a bit more space. Male gouramis are the more colorful and also the more belligerant of the two sexes. Do not get a pair if they appeal as a "threat" fish. Make sure there are some real of fake lants in the tank as well so the schoolers can hide if they get really freaked out.
I should mention I am not a fan of glowfish. But that is just my personal opinion. However they are a genetically engineered version of several species including danios, tetras, barbs and some more I am sure. Do yoiu know from which base species your glofsh are?
If you can, I would pick just one species of the shchooling fish you have, or a different one entirely, and then, based on their size, you can keep at least 6 or more depending on the max. size of the species you choose. I am assuming your water is OK for the fish. If you are not sure, you can ask here.
It is not required to have a 'threat fish" with a group of schoolers. You will still see them school at times, meander at times and during feeding its every fish for itself.