“I went overseas and left a large, well-fed (maybe overfed) Discus tank with no water change for 2 weeks. I tested for Nitrates the night before I finally did a water change and they were under 5ppm. Maybe it wasn't the 2 Black Bricks in my sump but I won't be running a sump without them from now on. This pack I just purchased is for a second sump.”
