One Of My Male Dwarf Gouramis Is Not Eating, Looks Sick

[epicson]

I have 3 male dwarf gouramis in a 29 gallon tank planted tank. One of them is not eating and is not very active like usual. He just sits on the bottom of the tank in the corner or in places he never usually goes. He looks ill to me. When I go to feed all the fish, the other two eat, but he does not eat (even if flakes are right in front of his face). He used to eat fine just like all the fish have, but for some reason not eating now.
 
I tested my water parameters and wondering if something is going on with my water or if anyone else knows what could be going on.
 
Here are my tests:
 
PH 7.8
Ammonia 0.50 ppm
Nitrite 0
Nitrate 5.0ppm
 
 
Could it be that just he is sick for some reason and the others are ok? I'm wondering what I should do to try and save him. Should I put him in a quarantine tank and if so, what is the proper way to do that?
 
 
 
 

 

[Ninjouzata]

How long has the tank been set up? How did you cycle it? Since there is ammonia it sounds like the tank isn't cycled or it's a false reading.
 
I wonder if he is beginning to suffer from DG disease. I would QT him as if that's it then it can spread to the others. He could just be stressed from being around the other males though, they can be territorial.
 
To set up a QT tank you'll want another tank, heater, and filter if possible. If you can't do a filter then you'll want to do daily water changes. Best as bare bottom so you can check their poo and spot clean more easily.

 

[WILDER]

What's the make of the test kit you are using please?
How is the fish?