First check your salt. As soon as you buy your salt it needs to be mixed it settles during shipping.found that out a few yrs back when a my numbers were off. I open the box and put it in another bucket and mix all the dry salt..and it turned out to be the salt not mixed good enough. numbers are good now. Now i mix it as soon as i get home so its ready to mix with water when i do water changes. Also when nitrites fall due to consumption of organisms reduction in nitrates of 50ppm will "increase " alkalinity by 2.3 dkh.to much alkalinity can result in reduction of calcium. So check your calcium. On the flip side to much calcium will drive down alkalinity. Vibrant is a great product several people i talk to are not aware there are 3 different formulas of Vibrant... reef tanks, freshwater and Saltwater for fish only tanks. Just thought I would put thatvput there