Option- Of course you don’t include enough information to really figure out what the problem is. Try this: Do several small water changes with high quality salt (I like Kent). This will fix any trace element problems you may have like low Magnesium, which will drastically affect the solubility of calcium and bi-carbonates, without having to go out and buy 10 new tester kits and supplements. I recommend doing a 5% change every day for 7 days. This will reduce the shock to your system of a larger change. Be sure to “age” your new salt water at least 24 hours, preferably 72 hours, before using it to allow the ph, oxygen, and carbon dioxide to all stabilize, this is true even for the “instant ocean” salts which claim they can be used immediately after mixing. I do this in a 5 gal bucket out in my garage. Right before you take the old water out, take a turkey-baster (clean one) and “stir up” all the detritus that has settled down into the cracks of your live rock and base rock. (This could be the cause of the falling pH and dKH) With it all stirred up, you will be able to get some of it out when you do the water change. This will cause a temporary cloudiness, but if you have any fine filter feeders, like feather dusters, they will actually like it, and it won’t hurt your fish or corals. After that week, if you still have problems, we will need more information to help you. Some things to look at: How old is your filtration, what type of substrate do you have, what species are you keeping, what kind of skimmer are you using, how often do you use it? Any and all of your water parameters will be helpful as well. Hope this gives you a starting place, good luck.
