If it contains sulfur eventually it’s acidic In my experience. So just tested and leaving everything alone now I still get 20alk but ammonia is 0-0.1 hard to tell on api, nitrate dropped from ten to 5.7, phosphate is still zero though that’s gfo working. I know my old rock is leeching. Ph holding in at 8. Being a fish on,y for now that’s going be fine. I’ll let it go a few Weeks and I think it will stabilize. I’ll not change out gfo and see what happens. These rocks are 15 years old. Anyway im not sure what prime did other than increase alk and lower ph. I would not use it again. There is no better solution than large water changes in my opinion. I did my experiment this morning using fresh saltwater and dosing ammonium chloride. Didn’t mess with test kits. Added prime and oh brother nothing was right. Ph went off, alk jumped, ammonia stayed same. I dosed nitrate and that looked way low. I have no way to nitrite but I think that would read low too. Someone with time should repeat this Unless it was on pages 7-32. Got tired of the flame wars.