Try pouring gallon of bleach, has to be bleach that has at least 7.5% sodium hydrochloride, if doesn't have a % on the label dont use it, with the pump on pour the bleach super slowly right at the water output AFTER SUNSET. The bleach doesn't have stabilizers like pool chlorine does and therefore it works immediately and that's why the slow pour is important. By morning that bleach will have done its job and be gone therefore not affecting your chemical levels but resulting in sparkling clean pool. Make sure to backwash or clean filter the next morning and then run your pump for 2 days straight using the bleach again if any cloudiness remains. Once the water is clear just pour half gallon bleach every few nights and run pump and your pool will stay clear. Just remember the bleach is immediate and then gone. It's doesn't replace chlorine it just helps it out so keep your levels of chlorine as usual. Once our of hot summer months the chlorine will be able to its job alone again. I promise this works. And please no "chlorine is chlorine bleach is no different" comments because it's not true. They work differently. Try it and let me know when your sparkling clear again, 3rd morning after 1st gallon of bleach I guarantee it!