Sudden Alk & calcium inbalance

phixman · Jul 16, 2020

For as long as I have been dosing (3 years) I have dosed equal parts of both calcium and alkalinity. A few months ago I added a rock with a lot of sps which was probably a 200% increased in sps, I increased my daily dosing from 50 mls of both to 75 mls to accommodate this for both Calcium and Alk. On July 9 I saw an uptrend and knew I'd have to decrease my dosing, I tested today and alk had spiked ( I retested to be positive), calcium also had plumited from 450 to 400 even though I'm dosing equals parts so they both should of risen? Anyways I adjusted my dosing - Alk from 75 to 55 and calcium from 75 to 90 to try to rebalance them.

What can cause an imbalance like this to happen?

Randy Holmes-Farley · Jul 16, 2020

Two things most likely to cause this observation are

1. Mismatched dosing (pumps not delivering what you think, tubes clogged, fluid ran out, etc.)
2. Test error

Nitrate dosing or a big nitrate decline will boost alkalinity.

Water changes with a salt mix not matching the tank can do it.

phixman · Jul 16, 2020

Hi Randy,

Say I've been dosing an alk solution with concentration of 20 (this is a random number) , and same with calcium which keeps them balance.
If I were to dose a new product with a concentration of 30 for alk , but 20 calcium. Alk would rise, but what about calcium? Will it drop or stay stable like it was before?

Randy Holmes-Farley · Jul 16, 2020

phixman said:
Hi Randy,

Say I've been dosing an alk solution with concentration of 20 (this is a random number) , and same with calcium which keeps them balance.
If I were to dose a new product with a concentration of 30 for alk , but 20 calcium. Alk would rise, but what about calcium? Will it drop or stay stable like it was before?

That's a somewhat complicated question.

Higher alk drives higher alk and calcium usage, both b corals and by abiotic precipitation. So increasing alkalinity increases the demand for alk and calcium, and if you do not increase the calcium dosing to match, calcium will decline.