I like the ecobak brand, been using them for years now and recently switched to their ecobak plus formula and it's working great. Make sure they tumble nicely, good rolling tumble but not too violent... make sure you start with 1/2 the recommended amount on the bottle and slowly add more after a month or so if needed. Make sure the output is either plumbed directly to the skimmer (a pvc T-fitting works great) or at least in the skimmer compartment in your sump.Hopefully that's not one of my frags STNing. I'm a big fan of superglueing the STNing flesh and a little above it too stop the STN.