I am a beginner. I have had my freshwater fish tank for a month now. My tank has a filter and heater. I have three female platys. I also have two plants, a ship, barrel and one plastic plant in it. I treated my water with water conditioner. I also test my water, quality is safe and is where it needs to be. I've have changed the water three times so far. I also feed them twice a day. My platys recently started hiding in the ship and behind one of the plants. They do swim around sometimes and eat just fine. Today I have noticed white cotton like stuff growing on the base of my java Fern and the stuff is also on the uneaten food floating around the tank. I believe I am overfeeding. My question what is the cotton like stuff in my tank? Is it harmful? What do I need to do to get rid of it? I will post a picture of it. I have researched a little and some say it is fungus and I need to get rid of it and some say it is safe and not to worry about. Very confusing.