New aquarium

Question
Hello! I am a first time fish owner and I am worried about my new fish. I "inherited" them from my boyfriend who is switching to Discus fish. I have a 20 gallon tank with 2 Sliverdollars and 2 Powder Blue Dwarf Gouramis. They all previously lived with 2 other gouramis that were very aggressive and stressed the Sliver dollars. When I received them the Sliverdollars had hardly any fins left. Since moving them to my apartment in the new tank, the Sliverdollars and the one Gourami seem to be doing much better. However, the other Gourami lays on the bottom of the tank in the front corner, away from the plants and swims to the top, gets some air, blows a bubble, and swims back down to the bottom. It does this all day long. I asked my boyfriend and he said this is what it always did, but I am concerned it is actually a water temperature problem or something more serious. The other Gourami stays at the top, in the corner, behind some taller plants. Sometimes, it looks to me like when the one swims towards the top the other chases it back to the bottom, but I have so little experience with fish that I am not sure. I also watch the fish eat after I feed them and it seems to me that the bottom Gourami does not eat anything. I am feeding them TetraMin. I don't know if the fish is still stressed from the move, or adjusting to the new tank, but I want to keep them happy and healthy, especially now that they are in a calmer environment without the extremely aggressive Gouramis. I appreciate your help and let me know if there is any more information I need to provide.

Answer
Hey Rebecca =]

It can't be a temp problem or a water problem as the others would act like this aswell.

You say the other one chases it, I think the more active one is a male and is bullying the smaller one which is a male I think because of the bullying.

I would take out the weaker one and put it in a 10 gallon.

I would also get rid of the other gourami as when the silver dollars grow (they grow huge!) they will bully and chase the blue gourami.  The two silver dollars will be great together :)

Hope this helps and Good Luck    Jack :)