I have 17 gallon qt. Ammonia was at 0 yesterday now at 0.50. How much water to change. Treating with coppersafe. What such a increase so fast. One watchman gobie 5 in long, one hippo tang little bigger than silver dollar, one fire fish 2 in and one lunar wrass 4 to 5 inches. Didn't even feed till this morning quarter cube of frozen brine. My filter is doing 60 gallon an hour that's the best I got. I just cleaned the filter.