Thanks. The problem is I can't take him back. My dad took him when he was getting some plants from some person, and she/he made him take the Gourami to. I put him in the tank, and there was a big problem. Every single one of the fish (betta included) started acting up. This is probably because he/she (I do not know) was so big (three inches). I'm not going to put him in the other tank, since the guppyes will be scared out of their wits. What I did was I put him in a bowl for now. It's probably about 2-3 gallons. I know that this is way too small, but at the moment I'm stuck with him/her, so It will have to do for now. I will get a 15 gallon soon, and I will put more fish in it.
About the guppys and the betta. I started keeping a pair of guppys with the betta when I was new to the hobby. I quickly learned that that was wrong, But the betta I was keeping the guppys got along with them fine. I've been doing this for about 2 years, and for some reason this betta doesn't mind. He's ancient (2.5 years), so that might have something to do with it. I'm not going to put guppys with another betta, but with this betta they do fine.
About the Gourami, he is whitsh grayish with blueish grayish stripes, apeares active and healthy, and Is three inches. I'm not sure how to tell how old it is, or if It's a he or a she, or what kind it is. If anyone knows how to tell, please tell me.
I don't have a heater, so that could be a problem...
thanks for your help
UPDATE: I will be giving him/her away. I just want to keep him/her alive before I do.
UPDATE: serious trouble. It (he/she) has some sort of parasite (I think). It has some red dots on his forhead. I'll keep watch on my other fish. I'm not sure If that Is a parasite, but It was rubing on something, and It swims backward. I'm not going to give away a sic fish. Also, It's not eating. Please Help!