Black Molly Acting Strange Lately

[joselaz5780]

About 24 hours ago, I noticed my black molly on the bottom of the tank(still breathing) and I decided to do a 25% water change. I performed the water change and fed the fish and the molly came up, ate swam around a little and then went back to the ground. Now he is laying on the floor against a plant and still breathing. I am thinking a 50% water change? I don't really know what to do. What is wrong? What can I do? Is his time up? He's not laying down horizontally, he's just laying there normally but on the ground. I bought him as an adult about one year ago, so I'm estimating he's about one year and like 8 months.