Shock & Clarifiers
A hot tub shock (or oxidising) product removes dissolved organic matter and non-filterable waste from the water, including perspiration, urine and decomposing flies.
All of these nasties provide a great source of food for harmful bacteria and will quickly lead to both cloudy water and the need for more and more sanitiser to be used. So, it's important to use a hot tub shock regularly to remove dissolved organic contaminants.
A water clarifiers is different from a shock. A clarifier 'polishes' dull water by removing small suspended particles that can cause cloudiness. They work by coagulating tiny particles, that filters ordinarily cannot capture, into larger ones that can be trapped in the filters and then removed. Clarifies usually work well on cloudy water that is caused by limescale.
Unless your teenage kids have had a party, if your water starts to go cloudy be suspicious of your filter first. How old is it? How are you cleaning it? Read about hot tub filter cleaning
Anti-foam is OK as a quick fix but it won't remove the contaminants that are causing the foaming and it will make the water dull. Always try a shock treatment first to cure foaming.