High Calcium / Magnesium - Why is Alk Dropping?

[RobberyinCSharp1824]

I have a 20g reef aquarium with 2 turbo snails, some soft corals (zoas, palys, mushroom, just added a birdsnest coral a few days ago). I perform a 2-part dosing from Seachem Prime to support Ca/Mg in the tank. I dosed about two weeks ago and the measurements were high (Ca = 485, Mg = 1335) and my Alk was 10.3. I test Alk with a Hannah checker and Ca/Mg with Salifert testing. Today, my readings were Alk = 8.17, Ca = 475, Mg = 1380. I'm kind of surprised that over two weeks my Mg went up and my Alk is dropping - is that normal? Is there a reason that happened, and is there a way to bring up my Alk without continuing to dose any of these nutrients?

 

[Spare time]

Prime doesn't do anything for Calcium or Magnesium. Prime is a dechlorinator and has nothing to do with major elements. To raise alk you need to dose an alk supplement or do water changes. Stony corals will drain alk from the water as welk as coralline algae.

 

[Fishbro]

Yeah if you’re saying you’re using Seachem prime that’s a dechlorinator but maybe you mean you’re dosing a two part from Seachem maybe? Alkalinity is consumed at a much faster rate than magnesium and still faster than calcium, currently in my tank my calcium is barely dropping, but my Alk going down 1 dkh a week, kind of the same as you. I think it’s normal but for magnesium going up that could just be a testing error and it just hasn’t gone down at all.

 

[RobberyinCSharp1824]

Prime doesn't do anything for Calcium or Magnesium. Prime is a dechlorinator and has nothing to do with major elements. To raise alk you need to dose an alk supplement or do water changes. Stony corals will drain alk from the water as welk as coralline algae.

Yeah if you’re saying you’re using Seachem prime that’s a dechlorinator but maybe you mean you’re dosing a two part from Seachem maybe? Alkalinity is consumed at a much faster rate than magnesium and still faster than calcium, currently in my tank my calcium is barely dropping, but my Alk going down 1 dkh a week, kind of the same as you. I think it’s normal but for magnesium going up that could just be a testing error and it just hasn’t gone down at all.

Sorry, I misspoke. Its not seachem prime. Seachem FUSION is what I meant to say!

 

[Randy Holmes-Farley]

Seachem Reef Fusion is not properly designed for 1:1 dosing. It's a very strange mistake by Seachem.

In general, I would dose enough of both parts equally to maintain alkalinity, and expect to need to dial back the calcium part if calcium starts to climb.

This has more on that imbalanced design:

Seachem Reef Fusion is not properly alk/calcium balanced for 1:1 dosing

A recent thread in the chemistry forum from someone who found that calcium increased with this product while maintaining alkalinity and using 1:1 dosing as advised by Seachem provoked me to check it's manufacturer specifications to see if it was a balanced additive. From Seachem's claims about...

www.reef2reef.com

 

[Randy Holmes-Farley]

The magnesium changes you see are either test error, or salinity changes. Neither the consumption nor that product have enough magnesium to cause substantial changes in a week.

 

[Mele__Reef]

I have reached to seachem in the past back when I had a freshwater cichlids tank. I soon discovered that Prime lowers PH. I always had a hard keeping the ph up for this reason. This may be part of your problem. have you tested PH?

 

[blasterman]

I have a 20g reef aquarium with 2 turbo snails, some soft corals (zoas, palys, mushroom, just added a birdsnest coral a few days ago).

Robbery - stop obsessing over calcium and magnesium. With that load of coral it will take months for calcium to drop to corrective levels, if not longer. A water change will likely reduce calcium more than corals given that most salt mixes don't run calcium that high, so you are literally trying to pour water in a bucket with a hole in it.

Just my embellished opinion, but calcium levels over 400 won't grow corals faster and even the most finicky SPS don't care about precise calcium levels. Target your calcium levels for 400'ish range, or whatever your salt mixes at and concentrate on dKH, which does matter. Stop trying to balance your dosing because you won't succeed because you don't have enough stony corals to consume things at a balanced ratio in the first place. Balanced dosing kits are darn near an oxymoron unless you have a big, stable tanks with lots of SPS.

One of my frag tanks is 10 gal and has 100x the mass of SPS growing in it than yours, and it consumes 1 full point of dKH a night. Calcium only requires correction every couple of weeks. I would go nuts trying to run a two part on that tank.

 

[RobberyinCSharp1824]

Seachem Reef Fusion is not properly designed for 1:1 dosing. It's a very strange mistake by Seachem.

In general, I would dose enough of both parts equally to maintain alkalinity, and expect to need to dial back the calcium part if calcium starts to climb.

This has more on that imbalanced design:

Whoa - good to know! To be honest, my Salinity is staying level at 1.023 unless my refractometer is busted. I just checked it against some RO/DI water the other day and it was 0. I run an ATO as well to try and keep salinity stable. Perhaps my salinity is too low to maintain a high alk?

Robbery - stop obsessing over calcium and magnesium. With that load of coral it will take months for calcium to drop to corrective levels, if not longer. A water change will likely reduce calcium more than corals given that most salt mixes don't run calcium that high, so you are literally trying to pour water in a bucket with a hole in it.

Just my embellished opinion, but calcium levels over 400 won't grow corals faster and even the most finicky SPS don't care about precise calcium levels. Target your calcium levels for 400'ish range, or whatever your salt mixes at and concentrate on dKH, which does matter. Stop trying to balance your dosing because you won't succeed because you don't have enough stony corals to consume things at a balanced ratio in the first place. Balanced dosing kits are darn near an oxymoron unless you have a big, stable tanks with lots of SPS.

One of my frag tanks is 10 gal and has 100x the mass of SPS growing in it than yours, and it consumes 1 full point of dKH a night. Calcium only requires correction every couple of weeks. I would go nuts trying to run a two part on that tank.

Fair enough. Many years ago before I took a break from this hobby I failed miserably at keeping SPS, and one of the things I noticed is that my calcium and magnesium levels were quite low. I did water changes, had a decent light, but they always died. I figured my nutrients were the problem.

 

[Rybren]

You need to calibrate your refractometer using a calibration fluid and not RODI. In addition, I would personally bump up the SG to 1.026 (using a proper calibrated device).

 

[Randy Holmes-Farley]

Whoa - good to know! To be honest, my Salinity is staying level at 1.023 unless my refractometer is busted. I just checked it against some RO/DI water the other day and it was 0. I run an ATO as well to try and keep salinity stable. Perhaps my salinity is too low to maintain a high alk?

No, a sg of 1.023 should be fine for any normal alkalinity.