Hi! I own a 18x 36 inground with a vinyl liner, depth from 3.5' to 4.5' and use a cartridge filtration system with a Nature2 cartridge and add liquid shock once a week. I'm not having any water issues and have had my pool for four years.
I don't have a heater so my season is only from the end of May to the second week of September. No questions right now, just introducing myself.