Hey guys! I'm Gustavo, and recently I decided to get back into the hobby of having fish. I decided to buy a very pretty Dumbo Halfmoon male betta (alongside everything needed to care for it) and, thinking that I already have a nice 1-gallon fish tank at home, I put Chucho (that's the name of my betta btw) in it. I noticed Chucho was flaring a lot towards the sides of the tank, and when I went to study that I found that the sides of the tank were completely fogged up, and even acting as a two way mirror (albeit Chucho could only see himself in the sides, but I could see him) this resulted in Chucho flaring all the time and even charging at the glass. Even the front and back sides of the tank are a bit foggy. Apart from covering up those sides (which I will do as a temporary fix soon) how could I clean this old tanks' sides in a way to make them good as new?