ok, i purchased HTH pool salt from walmart and it says that it treats up to 20,000 gallons. my pool is only 5,061 gallons (16ftx48in).....im confused as to why the salt would say that and then the instruction manual says i need 125lbs of salt for my size pool....what is going on??? I'm new to all of this. I have no idea what pool school is i have just read the instructions everything is connected and ready to go i just need to know how much salt i need and what other chemicals i need for the other levels.....my pool currently looks swampy it definitely has algae...should i empty it out and refill it? or is there a way i can save it? I'm super lost...