This stuff is amazing for cleaning! I use a mix of this in hot water, dissolve and add hydrogen peroxide and spray on my tub scrum and hard water or mineral deposits. Then i leave the room and have the fan going the whole time. All you need is a wash cloth after that to remove the gummy grey buildup from the bottom of your tub, the walls etc. It's the only thing that works for an acrylic tub that won't scratch or ruin it. Then I use some automotive wax to seal the tub again and rain x on the walls... This works to prevent build up for about two months. Soapy washcloths can manage in between.
Now, for an insane cleaning tip. Use 1 tsp to two tsp of this in addition to your regular dishwasher detergent and watch hard water scum disappear from your dishes and washer forever. Use an eco friendly detergent and you won't need to fear residue on your dishes and glasses again. I thought my dishwasher was a piece of junk and didn't use it for a few years before I tried adding this. The dishes always came out dirty and filmy and awful without the citric acid. I gave up trying different cleaners and hand washed everything...very laborious. Now I can use my dishwasher again with great results. My glasses are so clear!
Citric acid is my go to for cleaning, but wear gloves and have good ventilation for the hydrogen peroxide mix i mentioned.
I like this brand because it's food safe and I can also use it in canning and to add to food stuffs or sub for lemon juice in some cases.