Calcium not being consumed

[TastyScrants]

My calcium levels are not dropping, they have been consistently at 465ppm for 2 weeks. I’m more concerned that my corals aren’t consuming much calcium than the actual level it’s at.

parameters
temp 26°C
Salinity 35.2ppm
Nitrate 1ppm
Phosphate 0.04ppm
Alkalinity 8.6dKH
Calcium 465ppm
Magnesium 1380ppm

weekly 10% waterchabges using RedSea blue bucket.

tank volume 150L after displacement. I have many corals majority are LPS and SPS. I have coralline algae but not a large mass yet, it is everywhere in tiny deposits.

I was using RedSea 3 part on the accelerated parameters with alkalinity of 11.5dKH. I have been gradually reducing this down to 8.5dKH for about 6 weeks as I want to start dosing a 2 part product which recommends a lower alkalinity. As my tank consumes 0.2-0.3dKH a day I just stopped dosing to allow it to decrease.

Since I started reducing my alk my calcium and magnesium have barely changed, they were all being consumed consistently when I was running higher alk I had to dose all 3 each day to maintain my targets.

What can I do to correct my levels? My corals look happy but I’m concerned that a problem is just around the corner.

Thanks.

 

[Jonify]

My calcium levels are not dropping, they have been consistently at 465ppm for 2 weeks. I’m more concerned that my corals aren’t consuming much calcium than the actual level it’s at.

parameters
temp 26°C
Salinity 35.2ppm
Nitrate 1ppm
Phosphate 0.04ppm
Alkalinity 8.6dKH
Calcium 465ppm
Magnesium 1380ppm

weekly 10% waterchabges using RedSea blue bucket.

tank volume 150L after displacement. I have many corals majority are LPS and SPS. I have coralline algae but not a large mass yet, it is everywhere in tiny deposits.

I was using RedSea 3 part on the accelerated parameters with alkalinity of 11.5dKH. I have been gradually reducing this down to 8.5dKH for about 6 weeks as I want to start dosing a 2 part product which recommends a lower alkalinity. As my tank consumes 0.2-0.3dKH a day I just stopped dosing to allow it to decrease.

Since I started reducing my alk my calcium and magnesium have barely changed, they were all being consumed consistently when I was running higher alk I had to dose all 3 each day to maintain my targets.

What can I do to correct my levels? My corals look happy but I’m concerned that a problem is just around the corner.

Thanks.

The growth rates (in a stable tank, and all other things considered) between 11.5dKH and 8dKH are pretty stark. BRS did a test of this about 2 years ago. For their experiment, it was a little more than double the growth rate at the higher alk level, if I am remembering correctly. I say that to say, your calcium is going to be depleted more quickly at higher alk levels, because of the faster growth and higher coral consumption of calcium to achieve that growth. Going to lower alk, you're probably going to notice lower calcium consumption. And in the middle of a transition to a lower alk, it may stop altogether, because your tank is going through a destabilizing event, even if you're doing it slowly.

One other note--relative to alkalinity consumption, calcium consumption is much less. So it may take a week or two for you to notice exactly how much calcium is or isn't being consumed. Calcium consumption is ~18-20 ppm for each 2.8 dKH of alkalinity consumption. So if your tank is consuming 0.2dkH a day, the calcium drop is going to be about 1.5-1.8ppm a day. And you won't be able to measure that. It will take a couple of weeks for your test kit to show any real movement. Hope that's helpful!

 

[TastyScrants]

The growth rates (in a stable tank, and all other things considered) between 11.5dKH and 8dKH are pretty stark. BRS did a test of this about 2 years ago. For their experiment, it was a little more than double the growth rate at the higher alk level, if I am remembering correctly. I say that to say, your calcium is going to be depleted more quickly at higher alk levels, because of the faster growth and higher coral consumption of calcium to achieve that growth. Going to lower alk, you're probably going to notice lower calcium consumption. And in the middle of a transition to a lower alk, it may stop altogether, because your tank is going through a destabilizing event, even if you're doing it slowly.

One other note--relative to alkalinity consumption, calcium consumption is much less. So it may take a week or two for you to notice exactly how much calcium is or isn't being consumed. Calcium consumption is ~18-20 ppm for each 2.8 dKH of alkalinity consumption. So if your tank is consuming 0.2dkH a day, the calcium drop is going to be about 1.5-1.8ppm a day. And you won't be able to measure that. It will take a couple of weeks for your test kit to show any real movement. Hope that's helpful!

Very helpful, thank you.

I was seeing good results at higher alk but the new system I’m using has trace elements and magnesium in ratios within the 2 part so I needed to drop it (plus a lot cheaper). Maybe too soon to use if the calcium won’t deplete as fast as I won’t be able to get those traces in the tank

 

[Randy Holmes-Farley]

Very helpful, thank you.

I was seeing good results at higher alk but the new system I’m using has trace elements and magnesium in ratios within the 2 part so I needed to drop it (plus a lot cheaper). Maybe too soon to use if the calcium won’t deplete as fast as I won’t be able to get those traces in the tank

What exactly are you dosing? Many two parts are not intended to be useful trace element supplements, despite having them in it.

 

[TastyScrants]

What exactly are you dosing? Many two parts are not intended to be useful trace element supplements, despite having them in it.

At the moment I’ve just been dosing RedSea alkalinity while I wait for my calcium to decrease.

The product I have ready to start is called Reef Z-elements it’s a UK based company. This product specifically https://www.reef-zlements.com/z-complete/ on the UK based forums it’s been having fantastic results.

Prior to this I was dosing RedSea A, B, and C 3 part.

 

[Randy Holmes-Farley]

At the moment I’ve just been dosing RedSea alkalinity while I wait for my calcium to decrease.

The product I have ready to start is called Reef Z-elements it’s a UK based company. This product specifically https://www.reef-zlements.com/z-complete/ on the UK based forums it’s been having fantastic results.

Prior to this I was dosing RedSea A, B, and C 3 part.

It is not clear from that web site whether that product is supplementing trace elements, or instead just maintaining ionic balance (they do explicitly state the latter, but may not really understand what it means).

Note that containing trace elements does NOT mean the product increases them or offsets any consumption. it might even decrease them.

here's how that works:

The Many Methods for Supplementing Calcium and Alkalinity - REEFEDITION

There is no aspect of reef aquarium chemistry more important than calcium and alkalinity. Many of my previous articles have described various aspects of these systems in detail. In reading those articles, aquarists will note one pervasive theme: that maintaining appropriate levels of each are...

www.reefedition.com

One issue that has confused some reef keepers, however, is the presence of trace elements. Assuming that these products are actually formulated with every ion such that a true natural seawater residue remained (let’s call this the “ideal” product), then it will necessarily contain such ions as copper. Since copper is elevated in some reef tanks, and is toxic to many invertebrates, reef keepers have wrongly criticized this method as adding more copper. That’s actually not what would happen. Since these products leave a natural seawater residue, and since copper may be elevated in concentration in many reef tanks relative to seawater, then using these “ideal” products will actually LOWER copper levels because when the increase in salinity is corrected, the copper will drop.

For example:

You have copper in your aquarium at 4 ppb and salinity of S=35.

You add a two part additive that over the course of a month raises salinity to S=36, and raises copper to 4.02 ppb.

Then you correct the salinity back to S=35 by diluting everything in the tank with fresh water, and you get a final copper concentration of 3.9 ppb.

Does this happen in real products and not “ideal” products? I have no idea. But the statement by manufacturers that it contains all ions in natural ratios, including copper, should not be viewed as a concern that it is exacerbating a heavy metal problem.

The rise in salinity of these products over time can be very roughly calculated, though there are several reasons why this calculation is only an estimate. For every 1000 meq of alkalinity added in this fashion (and the matching amount of calcium) these products will deliver on the order of 60 grams of other ions to the tank. In a tank with a low calcification demand (defined later to be 18.3 thousand meq of alkalinity per year in a 100 gallon tank (0.4 dKH/day)) this effect will raise the salinity by 3 ppt per year (compared to a normal salinity of S ~35). In a high demand tank (defined later to be 219 thousand meq of alkalinity per year in a 100 gallon tank (4.4 dKH/day)), the salinity will rise by 35 ppt in a year, or approximately doubling the salinity. Consequently, the salinity should be monitored closely in using these types of additives, especially in a tank with high calcification rates.