Alkalinity/Calcium Consumption OFF

reefer1 · Aug 20, 2015

Hi,
I have noticed for a while that the rate of consumption in my reef tank is out of whack for these two compounds. (I honestly can't recall it being balanced for the two years my tank has been running. I just read though that this isn't correct.) I dose 15mL of alkalinity to 5mL of calcium daily. I also replace about 1.5-2 gallons of water through the ATO unit daily - can this be part of the imbalance?
Here are my tank specs:
105 gal display + 20 gal sump
Rowaphos running in reactor
T5/LED combo light
Salinity = 1.026
Temp = 77C
pH = 8.1-8.2
Alkalinity = 7.3dKH
Calcium = 415ppm
Magnesium = 1400ppm
Nitrates = 4ppm
Phosphates = 0
All measured with Salifert except Phosphates (Hanna Instruments)

Any information about what's going on or how to align consumption is appreciated.
Thanks!

redfishbluefish · Aug 20, 2015

First off, for a 105 gallon tank, your consumption is fairly low.....it's very low. So I'm assuming you have very few hard corals and/or small frags. The other consideration is the salt you're using and the amount of alk and calc in that....as well as the volume and frequency of those water changes.

I'm sure once the corals grow large or you have a bunch of frags, you'll see those numbers get closer together. And forget it if you put in a clam.

Hope this helps.

Oh, and your ATO has nothing to do with alk and calc....that should just be RO/DI water replacing that pure water that's evaporated.

Hausser · Aug 20, 2015

I dose 50ml of ALK a day and 5ml of calcium every other day. My tank uses ALK but very little calcium. Granted I have a 300 display with a 100 gallon sump. I do have 14 sps mini colonies and a few other LPS corals. How often do you do water changes and how many gallons are your water changes each time. What salt are you using.

Downbeach · Aug 21, 2015

The uptake of Ca and Alk, by “stony” type coral, coralline algae, etc. in a reef system is ~ 20 ppm Ca to 50 ppm(2.8dKH) Alk(CaCO3), which is a ratio of 2 pts Ca to 5 pts Alk (2:5). The other consideration is that there is less Alk in reserve in your system, so you'll see a greater impact on its uptake. As Paul said, your consumption is relatively low, and its likely that your "imbalance" with your dosing, is due to your WC's being better able to keep up with your Ca needs.

maroun.c · Aug 21, 2015

Many other factors go into play.
The concentration of the solution you're using can have a great effect. I use DIY 2 part dosing following Randy's formula and most of the time I have around 5-10 percent of the alk settle in the bottom.
Also dosing in an area without good flow can lead to precipitation of on element more than another based on ur levels.
Finally your salt can also change the balance if its not exactly where you want your parameters to be.

reefer1 · Aug 21, 2015

Here's some more information to answer questions above
Water changes are about 10 gallons every 10 days. I use Tropic Marine Pro reef Sea Salt
Dosing is in my sump near the return pump. I occasionally run a pump in this chamber to stir any detritus. I can run this continuously if you think it's needed.
I have a mixed reef. Most sps are 1-2". A couple are mini colonies 3-4". I have a starburst monti which is about 6" round. Very little sps growth - this is my concern. I have also have several favias, chalices, and a space invader pectin. These show more growth.
There's some coralline algae but a lot of it has been consumed by a couple of tuxedo urchins which are the backbone of my clean-up crew.
Thanks!

Randy Holmes-Farley · Aug 21, 2015

The primary reason for "out of balance" demand is salt mixes with excessively high calcium (some are over 500 ppm at 35 ppt). So you need to dose less calcium when using such a salt unless you are keeping it as high as the mix come sin.

I discuss such issues here:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

Randy Holmes-Farley · Aug 21, 2015

reefer1 said:
Here's some more information to answer questions above
Water changes are about 10 gallons every 10 days. I use Tropic Marine Pro reef Sea Salt
Dosing is in my sump near the return pump. I occasionally run a pump in this chamber to stir any detritus. I can run this continuously if you think it's needed.
Thanks!

So if you got exactly the parameters that Tropic Marin claims (7 dKH and 440 ppm calcium) then to get to your tank parameters (7.3 dKH and 415 ppm calcium) you would have to add an imbalance of calcium and alkalinity.

Specifically, you'd have to add the equivalent of 0.4 dKH of alkalinity every 10 days with no calcium. Then on top of that, whatever additional demand your tank consumes (and there are obviously a lot of assumptions in that calculation).

TD13 · Aug 21, 2015

Randy Holmes-Farley said:
The primary reason for "out of balance" demand is salt mixes with excessively high calcium (some are over 500 ppm at 35 ppt). So you need to dose less calcium when using such a salt unless you are keeping it as high as the mix come sin.

I discuss such issues here:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

Can I just tell you how much I love this guy!!!! How amazingly lucky are we to have someone around to explain the how/why of the water chemistry!!! Just amazing!