Calcium raised over night HELP

Reef craze · Dec 12, 2021

Tank is 110 gallons with sump. I tested last night then did a 20 gallon water change as per my weekly maintenance. I then tested again after lights out before bed. I haven't dosed anything in 4 days any idea what could of raised my calcium. Have lost 4 acros which were newly added to the tank as frags all other corals doing fine added 27 corals in total. Also skimmer is overflowing like crazy. Added last week. Thanks for the help in advance.

ReefEco · Dec 12, 2021

If you trust your test kits, and after testing again, and the only change you made was the water change, then I would start with that - test your saltwater, unless you just mixed 20 gallons and used all of it? Both your alk and CA went up, according to you readings. If you don't have any of the leftover saltwater to test, make a gallon from the same salt, mix it the same, and test it. If you are making only 20 gallons, it is possible that you scooped a part of the bucket/box that was not mixed well. But who knows. My first thought was that your salinity changed and the fresh saltwater was concentrated, but that doesn't seem to be the case...