The tank is full of bubbles because your presumably male betta fish is very happy with his environment. When a betta fish builds a bubble nest, it means the conditions are right for him to mate and he feels that his offspring will survive. There is nothing to worry about. This is a good thing!
After tap water is dechlorinated for fish use, it should be left to sit for a while so that the gas bubbles settle. If you don't do this, it will not hurt the betta, but bubbles will be apparent. They will go away in time.
Those bubbles on the surfface are a very good sign, your male betta is making a nest for a female friend. He is just letting you know, his life is good!
