I used to just drain mine and get down there with a shovel and hose to wash all the dirt out. Trying to balance your chemical and get rid of all the growing stuff is a nightmare. Better to just start over from fresh. If the walls feel a little or a lot slimy, that's bacteria growing. I used a high pressure water sprayer first with soap and a disinfectant then clean water. Remember to clean your filter and pump and disinfect.