Is this true?

mermaid_life · Jan 6, 2021

I read this today in another post: "...raise your calcium to about 460 ish, since your alk is so low. If you have lower alk, you can raise cal/mag to compensate. Right now, imo, you're starving your corals for growth..." Referring to a tank the keeps ALK around 7.5-8 and Ca at 415.

Is this true? I keep my alk 8.0 to 8.3. I keep my Ca at 420. My sps seems to be frozen in time. lol Little to no growth. I just wanted to double check if this could be a possibility for what I'm experiencing.

Thanks!

ShepherdReefer · Jan 6, 2021

Hello, my alk levels are 8.0-8.5 with ca around 420-440 but we do not have sps corals.

taricha · Jan 7, 2021

lynncgo said:
I keep my alk 8.0 to 8.3. I keep my Ca at 420. My sps seems to be frozen in time. lol Little to no growth. I just wanted to double check if this could be a possibility for what I'm experiencing.

It's not true that high levels of one Ca/Alk will "balance" low levels of the other. They are consumed in essentially a set ratio in all calcification that happens in our systems.
Those Ca/Alk numbers of yours are very typical and fine. They are not the reason for what you describe as slow coral growth.

Randy Holmes-Farley · Jan 7, 2021

lynncgo said:
I read this today in another post: "...raise your calcium to about 460 ish, since your alk is so low. If you have lower alk, you can raise cal/mag to compensate. Right now, imo, you're starving your corals for growth..." Referring to a tank the keeps ALK around 7.5-8 and Ca at 415.

Is this true? I keep my alk 8.0 to 8.3. I keep my Ca at 420. My sps seems to be frozen in time. lol Little to no growth. I just wanted to double check if this could be a possibility for what I'm experiencing.

Thanks!

No. Calcium is not a limiting factor for growth in corals when it is above 400 ppm. Alkalinity is the limiting factor for skeletal growth, and nutrients and light are limiting factors for tissue growth.

Same for magnesium, except perhaps with coralline algae that uses a fairly high proportion of magnesium relative to calcium, higher magnesium may possibly encourage it.