Algae? Mold? Who knows

Question
Hello Mr. Johnson, I am keeping a small freshwater fish tank (2 US. gal) as an experiment on closed ecosystems. However, I recently noticed that my water had gotten slightly cloudy. On closer inspection I noticed that hanging suspended in the water were thousands of tiny things that I could only describe as little spots or balls of white mold. I then noticed that these hair things were also covering all my shells, rocks, and (live) plants. They are almost invisible and very hard to see. They seem to be affecting my fish (two Cardinal tetras) as they are listing to one side and are not as active as they used to be. The water temperature is average for a tank of tropical fish, however there is no heater because I am trying to be as natural as possible. Instead my plants are acting as a filter. I have 2 ghost shrimp and 2 snails that seem to enjoy eating the stuff. I haven't done a water change in a couple of days and my tank is in front of a window and receives shaded sunlight throughout the day. Is it some type of mold? Or is it algae? Is it harmful? And if so, how do I get rid of it? Thanks for your help!

Answer
Ben,

 It sounds to me that you have algae growing in the tank. In my opinion, it is never a good idea to do experiments with live animals. The tetras that you have in the tank are tropical and need to have constant heat and not fluctuations. Keeping the tank in the window is the fastest way to get algae. It is also not good because during the day the tank is warm but at night the water temp is dropping dramatically and this is not good for the fish. The plants in the tank are in no way acting as a filter. The plants are adding oxygen to the tank but they are not filtering the water. With a tank that small with 2 fish, water changes need to be done at least every 2 days. The fastest way to get rid of the algae is to do water changes. You can also clean the tank walls and gravel and this will also help with the algae. Your tank is too small for the fish you have in it. I would recommend giving the fish the home they need by upgrading the tank.