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- Oct 24, 2016
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Hoping someone here might have some ideas... First a bit of background. The tank is 550 gallons with two 150 gallon sumps. Today when testing I noticed that the refractivity dropped from 34 last week to 24 this week. Also, calcium dropped from 450 last week to 350 this week. I took both of these measurements twice with different instruments. Alkalinity has held steady at 9.3 and pH steady at 8.3. The sump nor the tank have higher water levels than before. The skimmer has only pulled about 1 gallon over the last week. There were no water changes either. I have not found anything similar in anywhere on the web. Coral and fish all are OK. I’m completely baffled about what might have happened. Any ideas?