I don't know much about the Cory's but 1 Blue Gourami with the Tetras should be fine. I have a young Gold Gourami (the same as the blue) in a 20 gallon high with 5 neons tetras & 5 golw light tetras. There's also 3 fancy guppies, 4 Otocinclus, 1 Sailfin Molly and 2 black kuhli loaches. Yes, the tank is a bit overstocked but so far so good on the levels.................