I'm using Reef Salt by SeaChem. I'm using Sera test kits, and admittedly, am not terribly confident in its accuracy. I tested twice, and got between 5 and 6 both times, but I have had the tank up to 11 when dosing with SeaChem Reef Builder, but soon as I stopped it started dropping so something is still bringing down the Alk. I'm wondering if its the same decaying matter that is causing the phosphates and feeding all the algae in there, that's causing an issue with the alkalinity. My pH is steady as a rock at 8.3 however. I may want to get a different brand of test kit and see what it says before dosing, now that I have snails and crabs in there.
All other parameters are great though, so I would think I'd start having calcium issues if the alk was really that low.
Something is preventing my coralline algae from spreading, so its either the low alk, or the presence of phosphates that my test kit can't pick up. A month ago my phosphates were at 25ppm, and now they are undetectable. The algae is all brown and getting "melty" spots on it, so I think I'm about to kick the phosphate problem, but I expected coralline algae to start spreading when the phosphates got low.