Oscar illness

Question
Hi Megan,
i have 2 oscars who are about 200mm long, they are beautiful and i have had them for several years now.  in the last month my one Oscar has developed a swollen belly, and he tends to spend most of his time lying down on the bottom of the tank.  He has never had this occurrance before, however, he still eats regularly, but just looks down. (i know he is a male, and his female is also a bit "down" lately, but no visible problems can be seen with her) what can i do to help him?  they had "hole in the head" at one stage, but have been cured of that.  what can this be now?

Answer
Sounds like Hexamita (Hexamita is often mistaken for Hole in the Head). An effective treatment is the drug metronidazole. A combined treatment in the food (1% in any food the fish will eat) and in the water (12 mg per liter) is recommended. Repeat the water treatment every other day for three treatments