How do you remove algae from carpet?

You have to fumigate the house. Spray cans of fumigant are available at many hardware and pet stores; typically one can will do about 500 square feet (read the label). Plan where you are going to place each can, so that once you open it you need not go back into that room. Get all the people and animals out of the house, and then start blasting. Allow several hours for the stuff to work. You may need to repeat the process in ten days, as the sprays will kill adults and larvae but not eggs. And, of course, you will have to kill the fleas on your pets.