Natives and non natives

Question
I have two Guppies in my 5gal beginner aquarium. I also have 5 native minnows to the streem beside my house. The Guppies look like they are healthy and so do the minnows. I have been feeding the minnows some decent Quality fish food. The Guppies do not look as if they have not picked up any bugs from the minnows. I want to get a couple Leopard Corydoras into the setting but I dont know wether that would be a good idea? The tank is not heated but the water in the aquarium is about 72 degrees F, even when the A/C is on. How many minnows would I have to get rid of to make room for two corys? By the way, the minnows are only 1" long* and very skinny. Please respond. Thanx

Answer
You need at least 10g's if you are going to be adding more fish.  It's fine to keep guppies and minnows together as long as the minnows don't outgrow the guppies.  You should have a heater to bring the tank up to 75F.  Even if you got rid of the minnows, you would not have room for the cories, the tank is just too small, especially for schooling fish.