I had used it before in the past and I only done it once a week. You can do more, but you need a high nutrients export in your system if you’re going to do it.
Not for my tank. It is a 120 gallon fairy stocked mixed reef. My nutrients are pretty low, less than 5 nitrate and phosphates are around 0.03-0.05. I do skim pretty heavy and do frequent water changes.
I use 10mL a day in my 40G tank with a lot of zoas and mushrooms and have no algae issues. I probably only do a water change once a month and everything’s doing really well