I do not know if my rdsb had anything to do with it but my nitrates have dropped down to 2 . I had done so many other things to drop nitrates before adding the rdsb . Such as major cleaning of everything and upgrading my skimmer and of course major water changes to drop them. But after dropping nitrates to 4 from water changes they slowly climbed to 8,so it did not look like all the extra cleaning did the trick. Now that the rdsb is running they are down to 2. But at the time I added the rdsb the new skimmer was only in place about a week or so , and I also changed my skimmer media when I added the rdsb. So its either the new skimmer , rdsb, or calcium media change, or all three.