Woah. It seems to be in pretty bad shape. I would drain the entire tank, buy new sand, A LOT more rock, transfer the stock to the LFS
if they can hold it. Soak the tank in vinegar, rinse well.
Clean the protein skimmer... Probably get new lights... Fill it up with freshwater... Make sure everything works. Drain it again. Put rock then water then sand back in, re-cycle the tank, and get your stock back in.