Rinse after each use so it does not accumulate. I would use plain old white vinegar.
try bar keepers friend cleaner
I also like bar keepers friend for cleaning.
I use old used dryer sheets from the laundry, dampen them with warm water rub scum in circle motion, one small section at a time and wipe the residue off with dry towel, it will shine. Works on fiberglass, metal or glass.
Hi Hannah - This is the shower cleaner that we use to help keep grout and tiles clean and minimize the mildew - it works on kitchen grout too. Hope this helps! Hugs, Holly
PS - We have a FREE eBook with recipes for all of my homemade and all-natural cleaners. You can download it here --> https://pinkfortitude.com/thank#GreenClean