Alk issue in large system

ostrow · Mar 16, 2019

Randy,

I have a 220gal total volume system. Established thriving SPS dominated reef. I run a large calcium reactor. I have never had a problem with keeping levels balanced until now.

CA remains at 425 (Salifert)
MG stable at 1375 (Salifert)
Alk was always stable and balanced at 160 (Lamotte)

Lately alk crashes to 120. CA and MG remain unchanged. Confirmed with different kits.

How can this occur? What is the solution?

I keep adding baking soda. I've tried notching up the reactor output. I don't get how this can be.

Thanks.

ndrwater · Mar 16, 2019

Sounds like your corals are in a growth spurt. I've had it happen many times. Lower the pH in in the reactor a couple of ticks and see how things Ballance out.
I had the same thing happen recently after a massive fragging session. When corals get big enough to start affecting the flow to the middle of the corals they kinda seem to go a bit dormant. After I cut the corals back to allow more flow, the ALK demand jumped. I dropped the pH in the reactor a bit and all was right with the world again...

Randy Holmes-Farley · Mar 17, 2019

A 160 ppm to 120 ppm drop in alk would not show as a big drop in calcium (maybe 15 ppm) which you might not detect. So tweaking up the reactor or adding more of both seems like a good plan. It is not likely alk only.