Let's talk about Alkalinity, Calcium and Magnesium in an SPS Tank

I was battling high alkalinity and lowering calcium a few months ago so I decided to turn off my alkalinity dosing. I haven't had to dose any alkalinity with the bi weekly water changes since cutting off the dosing. I'm still dosing 16ml of calcium daily to keep it around 450. I also dose around 30ml of magnesium a week to keep it around 1400.

My alk is currently at 7.7 where its been the last few weeks. My calcium has crept up to 475 and magnesium at 1470 in the last few weeks.

Any idea what might be going on here? The tank is around 6 months old and has a few frags of sps and a few colonies of zoas.

Thanks!
 
You are just not using much Calcium in your tank with so little corals. looks like you could probably cut down the dosing.
 
JB NY said:
You are just not using much Calcium in your tank with so little corals. looks like you could probably cut down the dosing.
Click to expand...

Yeah I cut off the doser a few days ago and calcium hasn't really changed along with magnesium. My alkalinity on the other hand dropped from .2 dkh.

Should I leave calcium off and bring alkalinity back on for a few days and test?
 
Yeah just dose the alk for a little bit. Alk gets used up a little quicker than Ca, so you notice it sooner. You are probably using Ca too, just not enough to register on your test kit yet.
 
Yeah that is my issue, I have a calcium reactor but very little corals using up the calcium and ALk, so I turned the reactor off. I was testing alk @11. Holding very steady for 3-4 weeks. With little to no change in calcium I just shut it down until I get more stuff.

Corey
 
On ca/allk/ mag

On ca/allk/ mag

What is amazing in the Miami, Florida area there are docens of aquarium shops and no one ever told me to check my magnesium when I have been having trouble keeping my calcium and alkalinity levels from fluctuating to much. Was told to ad calcium buffers for low levels of calcium and vitamin c to lower alkalinity, when I finnaly have the magnesium levels check was told that it was at 1050 obviously low. Iam now trying to correct this slowly. A buch of bad advise giving.
 
Finpafine said:
hen I finnaly have the magnesium levels check was told that it was at 1050 obviously low. Iam now trying to correct this slowly. A buch of bad advise giving.
Click to expand...


Glad you got that Mg checked, yeah even LFS owners often don't know how important Mg is, sounds like you are on your way.
 
Very good thread! I wish i'd found it a week ago. I am in the middle of correcting my tanks params from 6.16 KH, PH 7.5 & Ca 580 (no mg test kit next purchase) I added probably way to much buffer at once yesterday and watched a snow storm for several hours. Water was clear but the precipitation lasted awhile. Which prompted me to google snow storm like search queries...

Results after Kh 9.5, PH 8-8.5, Ca 360 :O! I just added 30mg of mixed FM Balling Calcium mix to up the ca. My question is without a Mg test will I just be yo-yoing the kh and ca without much progress?

Most of the corals didn't seem to mind except the elegance didn't come out all day. Not a happy camper.

Sorry if I made some cringe reading this.
 
Last edited:
I would let it go another 24 hours and test again, so you have a better idea of what is going on in the tank. Yeah, pick up a Mg test when you can. But after 24 hours if you still have the same results, I would start adding CA to the tank and let the alk come down a little (8.5) then start using 2 part buffer but add more Ca then alk till you get things in line. Then take it from there.
 
Thanks JB!

I'll test at the same time tonight. And report back. My EC is slowly opening, though I think one of the hermits was all over it today as he was covered in zooxanthellae slime. I'm guessing came off of the EC when the crab walked all over it.
 
Tested last night 12:00 and again just now 5:40 pm.

Last nights results:
Alk: 7.28 Tested today. 6.72 (grr)
Ph: 8.0
Ca: 420

EC is happy, but i'm not. My small birds nest continues to bleach and his minimal polyp extension. All this testing and tweaking may just be its undoing.
 
Hey JB NY,
While I've only read a few posts of your thread, I see that you started it in 2007?
Nice thread!

On my system,
My alk runs 8-9ish (API)
Mag- 1470+ (salifert)
Ca+- 470+ (Salifert)
Had my Phos checked last week by local reefer- 0.0395...(Hanna Phosphate checker)
Nitrates- FEErrgett a bbouut it

I have a fairly large coral load, and about 270G Total WV
I use Kent Marine- and do 50g/month WC

I have no controller, no dosers, reacters, etc., etc.

After my research years ago, I only
use 1g RO/DI with:
60ml vinegar
25ml/cc Kalwasser
and drip it in to my sump over a few hours.

I also bolus add about 30cc of MgCl in a cup of sump water every two weeks.

THIS has kept my levels well and constant for years.

Reading some of the random posts though, I have to ask myself:
Why would you dose anything when doing watger changes, without any real demand/need?

It's like as BioCube 29 with a Ca Reactor!

Again, nice thread (I think), only read a few posts,
Todd
 
MidwesternTexan said:
Reading some of the random posts though, I have to ask myself:
Why would you dose anything when doing watger changes, without any real demand/need?
Click to expand...

You wouldn't doe if you have no real need. But this is in the SPS forum and the vast majority of people need to dose once their tank gets going and is filling up with stoney corals. A lot of the questions are from people with new tanks that don't have much demand and are confused on how to get their parameters in check.

But to give you an example. When my tank was full of SPS, my Ca reactor effluent was at 6 L/H, all my top off went through my kalk reactor, I used a full cup a kalk every 3-4 weeks and I did weekly water changes.
 
Even with water changes and few corals I still have a dosing pump for alkalinity to keep it very stable. My corals appreciate this immensely.
 
JB NY said:
Alkalinity.
...So my recommendation is to keep alk around 8-9 dKH for keeping acroporids. Another nice benefit of lower alk was less precipitate on heaters and pumps.
Click to expand...

So is this still the current line of thinking on recommended Alk levels? It seems like many tanks I see here, including many of the TOTM tanks are closer to 7-7.5 and some are kept under 7.

Also, when you talk about keeping alk steady, what is an acceptable fluctuation range? So for example, if I am shooting for 8.5, how much plus/minus would be acceptable without negatively impacting my corals?

Thanks!
 
I would still recommend people go with that level. This is a general topic and I think that you can have great success with alk in that range. Freshly mixed salt also tends to have a higher Alk level so maintaining lower levels can be difficult for some. When this thread first started I think the norm was to keep your alk around 12-14 dkH, so dropping it down to 8 or 9 was going against the trend at the time. Now, you are correct, many people keep their tank even lower.

I personally keep my tank around 8-8.2 I mention that someplace in this thread. Lots of people have decided to go lower, I have kept my alk closer to 7 for some time and felt that SPS corals, for me, did better around 8. On my tank if my alk falls below 7, I would take steps to get it back.

When the tank is stable, try to keep the alk very stable. +/- 0.2 it perfect IMO. But even I bounce around +/- .5 sometimes when I am adjusting things.
 
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