Suddenly Having a Lower Demand for Calcium

goldenhurricane2 · Apr 3, 2019

So over the last couple of weeks, my tanks usage of calcium has gone down a little (and a tiny bit with alk). Tank is mature (nearly 4 years old) with a little of all kinds of coral.

Any ideas on what may cause the sudden change in lower calcium demand?

Flippers4pups · Apr 4, 2019

Sometimes subtle changes can slow growth. Water parameters, lighting, nutrients....etc. Sometimes they just stall with everything stable.

Alkalinity dropping will have a effect on calcium up take. Swings like that will stall growth and may take some time to recover.

goldenhurricane2 · Apr 5, 2019

Flippers4pups said:
Sometimes subtle changes can slow growth. Water parameters, lighting, nutrients....etc. Sometimes they just stall with everything stable.

Alkalinity dropping will have a effect on calcium up take. Swings like that will stall growth and may take some time to recover.

Thanks - no big changes really, but that makes sense. The only noticeable changes in coral is my colony of green monti cap is a little pale, but otherwise everything is fine. I’ll just chalk it up to one of those things that just happens.

Randy Holmes-Farley · Apr 6, 2019

Most kits cannot accurately determine short term trends in calcium. I'd keep watching it. If alk demand is not changing, the calcium demand probably isn't changing much either.

goldenhurricane2 · Apr 6, 2019

Randy Holmes-Farley said:
Most kits cannot accurately determine short term trends in calcium. I'd keep watching it. If alk demand is not changing, the calcium demand probably isn't changing much either.

Alk demand has gone down slightly.

Auquanut · Apr 6, 2019

Not long ago, I noticed a slow decrease in calcium demand with no decrease in alk demand. I thought it was strange because all of my coral were growing well, and I thought demand of both should increase. Decided that I would wait until calc went to 480 before I made any change to my autodoser. Recently (within the past 3 weeks) both alk and calc demand have slowly started increasing. I have no idea why, but my unqualified opinion is to make no immediate changes as long as parameters are within acceptable ranges and let the tank figure it out.

Randy Holmes-Farley · Apr 7, 2019

There's no way for calcium to fall unless alk is declining in about the ratio of 18-20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity, except for things like water changes with a ratio not matching the tank, or something else is adding extra alkalinity.